Blog

Geologist A Geologist contributes primarily to the identification of leads and prospects for the company's international basins. They provide geological support for the producing fields from time to time. As a Geologist, they are required to perform play analysis, map seismic facies interpretation, sequence stratigraphy, and also evaluate petroleum system. They also generate prospects and develop new ideas including hydrocarbon plays. Also, one should possess good skills in identifying and reviewing geological, geophysical and other relevant data in developing geological models. Apart from conducting pre-drill planning, providing operational support, and undertaking post-drill geological evaluation of exploration drilling campaigns, a geologist also prepares and maintains prospects and leads inventories. In addition, they also prepare reports for each basin and permit area as required including geological risking and resource probabilistic estimations of hydrocarbons in place. Geologists also play a vital role in providing expert Exploration and appraisal Geological evaluations of assignments with an emphasis on resource assessment and proof of concept for conventional clastic reservoir plays. They need to have thorough knowledge of play and prospect identification, generation and development plus have a practical knowledge of resource estimation and risk analysis. Additional qualities that help to add value to this role are good abilities to drive and deliver projects for the team whilst dealing with a variety of stakeholders and disciplines, including subsurface - drilling and completions. It is paramount that they have strong leadership and mentoring skills which enables good collaboration with various engineering disciplines. Petrophysicist and Well Site Engineers Well site engineers and Petrophysicists  help in reviewing the existing processes and strive to improve drilling procedures including implementation of necessary changes. They require extensive seismic interpretation experience like 2D, 3D, structural and stratigraphic interpretation ranging from regional to prospect scale.  They utilize 3D techniques for robust fault mapping, trap mapping and seismic waveform analysis.  Apart from designing well profiles for multiple targets, they also present all work, prospects and proposals to their management, partners, and other stakeholders. Other aspects of this role include providing technical support and oversight for development geophysical studies and be able to mentor junior staff in geophysics.  They are also required to have excellent teamwork, interpersonal and communication skills. Communication includes collaboration within the company, recommendations to senior management and external representation of the company while working with partners and/or government representatives. Most importantly, they dedicate themselves to working at high technical standards, a passion for growth and the ability to form strong relationships with partners. Completions Engineers Develop completions basis for design, key design and procedure documents. They also form basis for execution plans and group loadings consistent with local policy and regulatory requirements. They utilize engineering tools and principles to assist in designing various aspects of a well completion. To ensure well objectives are achieved, they provide expert engineering and technology advice. They develop recommendations on equipment, materials specification, procurement and contracting. Other major aspects of this role include monitoring daily completion operations for HSE, cost, efficiency and completion integrity. Preparation of completion & workover programmes and cost estimates are also undertaken.  Mentoring and training  junior engineers is also a part of this role.  Strong interpersonal, team working and communication skills are the essence of this position. Drilling Engineers Drilling Engineers provide drilling engineering expertise for the design of exploration, appraisal, development and production wells. They supervise and mentor drilling and well engineers and prepare drilling engineering programs and execution procedures. Apart from assuring compliance with regulatory standards for well construction, they are also responsible for preparation of Government approval documentation. Another important task is to provide drilling engineering support to offshore rig teams and provide input in identifying and evaluating new opportunities. They require to collaborate with other engineering functions to resolve key issues and decisions. Reservoir Engineer A reservoir engineer researches, inspects, and evaluates underground oil and gas reserves to determine the most efficient means of extracting resources. He or she typically works on-site at an established well or a new drilling project, analyzing schematics and compounding scientific data. The information gathered is used to develop cheaper, more fruitful collection methods. Most reservoir engineers work for major petroleum corporations, though some are independent contractors or employees of government research or oversight committees. The daily job tasks of a reservoir engineer can vary depending on the project at hand. If a company plans on starting a new well, the engineer may first consult with surveyors and petroleum geologists to make sure the prospective reserve can supply enough oil or gas to make the job worthwhile. He or she then considers different drilling and extraction methods, and determines which will be the most cost-efficient. The resulting data and ideas are usually presented to supervisors for approval. Once a project is underway, the reservoir engineer helps to oversee drillers, construction workers, and scientists until completion. The finished well is monitored carefully in the first few days to make sure the amount of oil or gas extracted meets predictions. If problems arise, the engineer reviews schematics and orders repairs or changes to equipment. He or she typically checks on production numbers throughout the drilling phase, which may last months to years, to ensure good results. Seismologist Seismologists are Earth  scientists, specialized in geophysics, who study the genesis and the propagation of seismic waves in geological materials. Their research aims at interpreting the geological composition and structures of the Earth. The vast majority of seismologists work in petroleum exploration. Other seismologists study the seismic waves generated by much more powerful sources: natural, like earthquakes and mining events, or artificial, like underground nuclear tests. The fundamental work of a seismologist is to locate the source, the nature, and the size (magnitude) of these seismic events. Seismologists work in multidisciplinaryms composed of Earth scientists, technicians and professionals from the fields of computers, physics, electronics, telecommunications and civil engineering. Contacts with emergency organizations are often necessary. Workover Engineer The Completion and Workover Engineer monitors completion and workover activities and performs offset well production and completion analyses. Responsibilities include preparing the well proposal and basis of design for new well completions and workover activities and following the technical execution of programs. Make technical completion recommendations to achieve production optimization and also Prepare workover, completion, and recompletion well programs and end-of-well reports. In addition, they take part in well reviews to assist with diagnosis of well performance problem, and recommend programs for improvement or remediation of specific wells. Also, they perform engineering studies to solve recurring issues such as production performance, corrosion, and scale and to monitor well integrity. Logging (LWD & MWD) Logging engineers devise methods to improve oil and gas extraction and production and determine the need for new or modified tool designs. They also oversee drilling and offer technical advice. In addition, they assist engineering and other personnel to solve operating problems. They also confer with scientific, engineering, and technical personnel to resolve design, research, and testing problems. They require to direct and monitor the completion and evaluation of wells, well testing, or well surveys and also monitor production rates, and plan rework processes to improve production. Other aspects of this role involve analysing data to recommend placement of wells and supplementary processes to enhance product. Mud & Pumping Engineers A mud engineer works on an oil well or gas well drilling rig, and is responsible ensuring the properties of the drilling fluid, also known as drilling mud, are within designed specifications. Mud Engineers determine the Mud so that it meets specific area of requirements. They implement a series of Mud Tests After enrolment of their test results, Mud Engineers write  instructions for crew members so that they may then get started making key Mud treatments. If is necessary, a Mud Engineer might stay onsite to advise the crew members of the oil rigs and supervise methods for treatment.  Apart from standard responsibilities,  Mud Engineers are also accountable for creating Mud reports, ordering products for any treatments, and keeping field relationships. They have a diversity of responsibilities on the oil rig and hence Mud Engineers are known to experience high levels of  job gratification.  Cementing & Field Engineer Cementing Field Engineers deliver engineered solutions designed to ensure that the well is properly stabilized. The Cementing team employs the latest technologies and analytical software to ensure complete and proper cement placement. Cementing Field Engineers perform a variety of other services at the well, including providing technical and operational engineering expertise to external customers in a professional manner, leading the teams in implementing designs at the wellsite and assisting in pre-planning, job execution (at field wellsites onshore or offshore) and post-job analysis. They also interprete real-time wellsite data and work with software simulators and electrical and mechanical devices. In addition, they perform assignments requiring knowledge and application of basic engineering principles for design of work and promote safety awareness and environmental consciousness, and complying with all applicable safety and environmental procedures and regulations according to  Health, Safety and Environmental (HSE) regulations and guidelines. Well Control Engineer A well control engineer supervises assigned staff and is responsible for performing calculations and making assessments on well control problems both onsite and from the office. We are looking for a self-motivated individual that can effectively function as a member of a team, show initiative, and perform other duties as required for the team to be successful. Various tasks of a well control engineer include developing Blowout Contingency Plans, Relief Well Design, and related documents for a variety of customers. They require to travels to customer sites both domestically and internationally to deliver well control support to onshore and offshore locations. They also perform well control audits and conduct well control training on the job and in a classroom environment. Another task related to this role is to provide engineering support to field operations and assist with manual equipment setup and operation as required. Well control engineers also maintain appropriate reports and documentation of well site activities and periodically provide technical support on location to meets customer requirements. They also frequently advise staff and customers on equipment capabilities and keep management informed of significant problems. In addition to complying  with safety regulations, they provides assistance with or take the lead on activities such as:HAZID / HAZOP,Urban Risk Assessment, Emergency Response Planning, Emergency Response Drills, Blowout Contingency Planning and other duties as assigned or required. Well Test Engineer The Well Test Engineer forms part of a team that is responsible and accountable for all aspects of Well Test operations and activities covering planning, equipment, personnel and third party equipment. They are primarily responsible for supporting the day to day Well Intervention Operations and planning routine Well Test Programmes in line with company, safety and industry standards. They also ensure data is collected accurately and presented professionally to achieve a high quality report for the client. A well testing engineer is also required to liaise with Operations Supervisor (Onshore) to ensure they are fully aware of offshore/onshore operations. They also involve in compiling end of job report to required standard in a timely and efficient manner. In addition, they attends pre and post test Client meetings when required. Well testing engineers frequently assist in the onshore base, creating reports, packing kits etc. and actively participate in and promote company health and safety campaigns, policies and procedures.  Wireline & Perforations Engineer Wireline and Perforating Field Engineers use electronic tools and computerized surface systems at the wellsite to perform openhole, borehole seismic, and cased-hole logging to record and analyze subsurface formations in oil and gas wells. They also perform perforating services to facilitate the flow of oil and gas from the well. They are also required to perform Data acquisition and presentation. They help in development of client relationships and ensure work is carried out in a safe and timely manner. Fracture Engineer The Fracturing Engineer is responsible for providing overall technical and engineering management for the fracturing stimulation job and ensuring client's requirements are met. Specifically, their  duties include provision of technical and engineering management for the fracturing operation and organization and verification of all materials and equipment are at job site. They also prepare report, analyse and write recommendations. Fracture engineers also conduct control tests to ensure proper deliver of service and assist sales as needed to gather, analyze and report technical information. They are also required to comply with all government, industry and company regulations and standards to ensure a healthy and safety work environment and well as reduce environmental impact. Well Intervention Engineer In this role, you’ll be responsible for defining the control criteria and developing, evaluating and designing completions for both new wells and wells requiring intervention. You’ll determine the operating envelope and deliver solutions optimised for corrosion control and lifecycle integrity. You’ll also provide technical advice and detailed completion programmes to well-site personnel comprising appropriate hardware, fluids, services and procedures required for all completions. In addition, you may be required to spend time at the well-site supporting field staff and ensuring operations are performed in full compliance with company procedures, policies and guidelines. You may also be called upon to help-out with ‘non-rig’ activities including coiled-tubing, slick-line or electric line operations. Field Services Engineer A field service engineer conducts inspection of assembled equipment, to ensure proper installation. And also inspects all operating parts to ensure proper operation within expected tolerances. They tune and troubleshoot equipment for proper operation and interact with internal and external project managers during field projects. Also, They require to professionally interact with customer, regarding status of commissioning, on a daily basis. They help in  determining tools and equipment required to perform scope of job and perform routine maintenance on equipment, and assist in establishing preventative maintenance schedules with customer. In addition, they assemble, align, and install equipment as necessary. Operation Engineer Operations engineers are responsible for ensuring that their client's manufacturing systems work properly, that they comply with safety regulations, and meet the specifications provided by senior management. They also provide maintenance and support services and troubleshoot any problems that arise with manufacturing. Operations engineers can also assist management in improving the quality of their products and reducing production costs. They typically inspect and review operating activities and determine production schedules. An operations engineer also provides a multitude of services within either the construction or technological industry. These services can include maintenance, staff training, and investigations to determine the cause of defects.  Operations engineers often specialize in a particular discipline, which can require additional training.

A Abandonment Final plugging of wells, and/or permanent dismantling, etc. of a production platform or other installation. Absolute Pressure term used to describe the gauge pressure plus atmospheric pressure Absorption The ability of a gas, liquid or solid to attract and retain another substance without chemical combination. A quantity of such a substance that has absorbed as much of another as is physically possible is said to be saturated with it. Some refinery processes use this ability for instance to separate different hydrocarbons. Acidization is a process where by pumping techniques, acid is squeezed into tight and/or damaged reservoirs in an attempt to improve the well porosity and permeability and thereby improve the flow of hydrocarbons to the well. See also Stimulation Acid Rain  Develops when sulphur oxides (Sox) and nitrogen oxides (Nox), released by the combustion of fossil fuels (particularly coal) combine with moisture in the atmosphere to form sulphurous , sulphuric, nitrous and nitric acids. Because SOx and NOx are gases and because the formation of acid rain takes time, acid rain damage often occurs far from the source of the problem. Acoustic Log A record of the time taken by an acoustic (sound) wave to travel over a certain distance through the geological formations. Also called a sonic log. See also: seismic survey. Acreage Area covered by a lease granted for oil and gas exploration and for possible future production Acre-foot Unit used to measure the rock volume of an oil or gas reservoir structure. Additive   Chemical added to a product to improve its properties Adsorption A  separation process for removing impurities based on the fact that certain highly porous materials fix certain types of molecules onto their surface. Advance Payment Finance Finance for exploration and production provided in return for a first claim on production. Typical sources of such finance are U.S. refiners and pipeline companies. Aggregate                      The mineral matter used together with bitumen to create asphalt for road construction Air Gun                    Chamber from which compressed air is released to produce shock waves in the earth array is the most common technique used for seismic surveying at sea. Alcohols  A class of compounds, of which ethanol (the alcohol of beer and wine) is the best known. They react with acids to form esters. They are widely used as solvents. Aliphatic Carbons A group of hydrocarbon substances, including the Alkanes and most of the other fractions found naturally in crude oil. See Section 10. Alkanes                    Naturally-occurring paraffin fractions of which the molecules are based on a "straight chain" of hydrogen-saturated carbon atoms. See Section 10.       Alkylation A refining process used to produce improved gasoline components with e.g. lower pollutant effects, and also in plastics manufacture. Alluvial Fan A pattern of sedimentary deposit frequently laid down by streams or rivers where they spread out into plains. Alluvial fans from past geological eras are potential reservoir structures. American Petroleum Institute (API) API is the world's foremost authority on oil industry standards and practices. "API Gravity" is a reference system for the density of crude oils and constituent hydrocarbons. Ammonia   Manufactured by the direct combination of hydrogen an nitrogen under pressure over a catalyst. Anhydrous ammonia is mainly used for the manufacture of nitrogenous fertilisers. Anhydrous Without water or dried Anode See Sacrificial Anode. Anticline A fold in layered rocks originating below the surface in the form of an elongated dome. Anticlines make excellent drilling prospects since any oil in the deposit will naturally rise to the highest point of the structure because oil has a lower specific gravity than water. See also: syncline. Anticlinal traps      are essentially formed as a result of a folding of the strata trapping gas, water or oil contained in the reservoir rock. Anti Knock Compounds   Additives such as Tetra Ethyl Lead (TEL) and Tetra Methyl Lead (M) or Methyl Tertiary Butyl Ether (MTBE) which tend to prevent gasoline detonating ("knocking" or "pinking") under compression instead of burning evenly. This enhances their Octane Rating. Anti-pollution measures will in future largely eliminate lead based additives. Annulus The ring-shaped cavity between two concentric tubes-e.g. inner and outer strings of casing, or between casing, or drill pipe, and the well borehole. Apparent Earning Power (AEP) The apparent Earning Power of the MOD cashflow. A.P.I. gravity      An arbitrary scale adopted by the American Petroleum Institute for expressing the gravity of oils.  The higher the A.P.I. gravity, the lighter the crude (i.e. the higher the proportion of lighter fractions the oil contains). Appraisal well A well drilled as part of a programme to determine the size and likely yield of an oil or gas field. Appraisal Well. Before development, a discovery is likely to need at least two or three such wells. Aquifer   An underground formation of permeable rock saturated with water under pressure. For gas storage applications, an aquifer will need to consist of a permeable lower layer of rock and an impermeable upper layer (or ‘cap’), with a cavity for storing gas. Such formations may be, and frequently are, the same as those containing oil or gas reservoirs. Area of Mutual Interest (AMI)  Area where two or more companies agree to explore exclusively in concert. Aromatics Hydrocarbons with a ring structure, generally with a distinctive aromatic odour, and good solvent properties (e.g. BTX) Aromatic Hydrocarbons  The group of hydrocarbon products which include Benzene, Toluene, etc. and provide feedstock for many of the main petrochemical processes, as well as high Octane Rating gasoline blends. So-called from their "sweet" smell. See Section 10. Artificial Drive                    Methods of producing oil when natural reservoir pressures are insufficient or have declined, such as injection of gas or water into the reservoir structure. Articulated Platform                            A semi-buoyant structure anchored to the seabed by means of a "Universal" joint coupling which allows it to "sway" with the forces of the sea etc. Such structures need less rigid strength than fixed platforms and so are relatively lighter and cheaper to install. Asphalt                    A solid petroleum residue, similar to Bitumen, Tar and Pitch. Associated Gas   Natural gas found as part of or in conjunction with other constituents of crude oil, as opposed to such gas found on its own. The expression has come to include natural gas necessarily produced along with crude oil. ASTM                   American Society for Testing and Materials. In conjunction with the API and Institute of Petroleum, they publish authoritative standards and e.g. calculation tables used by the oil industry. ("ASTM tables"). Atmospheric pressure The weight of the atmosphere on the surface of the Earth. At sea level this is approximately 1.013 bars, 101,300 Newtons per square metre, 14.7 pounds per square inch or 30 inches of mercury. B Back Off 1. In drilling, to pull the drill-string out of, or partly out of, the borehole. To unscrew a joint of drillpipe. To slacken off a line or block. Ballast   Water taken aboard a tanker, semi-submersible rig etc. to maintain stability and to distribute load stresses e.g. in the case of part-cargoes. Modern tankers have segregated ballast tanks so that the water does not become polluted with oil. Barite                      A very heavy substance used as a main component of drilling mud, to increase its density (mud weight) and counter-balance pressures Barrel/Barrelage   A quantity of 42 US Gallons (approximately 35 Imperial Gallons). The traditional unit of measure of oil volume. "Barrelage" is a term for oil flow quantity measured by volume. See Section 13. Barrel oil equivalent (boe)                       a term frequently used to compare gas and oil and to provide a common measure for different quality gases. It is the number of barrels of stabilized crude oil, which contains approximately the same amount of energy as the gas: for example : 5.8 trillion cf. (of lean gas) approximates to 1 billion boe. Base chemicals                      Basic building blocks for the chemical industry, which are converted to other chemicals (e.g. aromatics and olefins converted into polymers). Basket A hollow tool used to retrieve junk from the well when fishing. The name is also sometimes given to the bird cage. Batter The inward slope of the legs of a steel platform for stability so that the foot of the jacket covers a larger area than at deck level. BCF or BN CF  Billion (109) cubic feet (cf), unit of measurement. BCN or BN CM Billion (109) cubic metres (cm), unit of measurement. Baseload The basic, underlying level of demand, or system minimum; used in the context of gas supply and power generation. The opposite of peak load. Beach price Price applying to gas at landfall, when water and liquid hydrocarbons have been removed. Bead The fused metal resulting from a welding operation or "pass" in a major weld, as in a pipeline. There are normally three, the root or stringer bead, the filler bead, and the cap bead. Bean A choke, the orifice in a flow control valve. To "bean up" or bean down" means to install a larger or smaller orifice, or to open or close a variable valve. Be    is the geological term defining a stratum of any thickness, and of uniform homogeneous texture. Benzene The simplest aromatic compound with a ring of six carbon atoms and six hydrogen atoms; one of the most important feedstocks for the chemical industry. Bentonite See Mud. Biodegradable     Material that can be decomposed or rotted by bacteria or other natural agents. Billion      In oil and gas usage, a billion means 101 not (One billion cubic feet (BCF) = one thousand million cubic feet). Biomass conversion      The conversion of biochemically derived material for the production of energy. Bird Cage     The small net-enclosed "platform" used offshore to transfer people by crane from e.g. boat to platform, or rig. Bit A drilling bit. Those chiefly in use are the steel roller- cutter, and the diamond-insert bit for hard formations, which penetrates by scratching or abrading the rock rather than by crushing or pulverising like the roller bit. There is also the annular diamond-insert core bit, for cutting and retrieving rock samples (in conjunction with a core barrel). As it rotates, it shears/crushes the rock strata away to form a well.   Most modern bits are comprised of three circular cutters (tricone), often studded with hard metals such as tungsten carbide. Bitumen    Extremely heavy semi-solid product of oil refining, made up of heavy hydrocarbons, used for road- building and roofing. A form of heavy, solid petroleum. See Asphalt Black Oil/Black Cargo        Crude oil, or distilled crude containing the fractions heavier than middle distillates. Black products    Diesel oils and fuels oils, i.e. products from the low or heavy end of the distillation process. See also: white products. Blind Rams See Blow Out Preventer Pipe Rams. Block 1. A licence or concession area. It may be almost any size or shape, although usually part of a grid pattern. An arrangement of pulley wheels used in lifting, on a derrick or crane. Bloom The rainbow-like fluorescence shown by oil for instance when floating on water. Blow Down 1. The process of releasing pressure in e.g. a refinery   pressure   vessel   by   venting  to   atmosphere. Primary production of a crude oil or condensate reservoir using the pressure of the associated gas. Blowout                          Uncontrolled or uncontrollable release of downhole pressure upward through the wellbore or casing. Although the main danger is fire, the gases are also toxic, and in floating operations a gas blowout may include a threat to the stability of the rig itself. (See Mud). Blowout Preventer (BOP) An emergency shut-off valve installed on the wellhead during drilling or testing of a well, which incorporates hydraulic pipe rams capable of closing the space around the drillpipe against very high pressures. Boomer                      This    expression normally  refers  to   a Compressed air, or electrical, source of sound used in marine seismic survey work. Borehole A well, especially referring to the face of the rock outside or below the casing. Test boreholes are also sunk to examine the suitability of a site for major foundation work, and to examine geological formations at points where no hydro-carbons are expected. Bottled gas                      LPG stored in the liquid state at moderate pressure in steel containers. Bottles                      1. Small pressure vessels of various kinds, especially to absorb pressure fluctuations. 2. Cylindrical flotation tanks such as those temporarily attached to a platform jacket during placement. Bottom-hole etc. The deepest part of a well, thus: Bottom-hole assembly (BHA) includes the drilling bit, drill collars, stabilizers and other drilling components run into the well on the end of the drillpipe. See Drill String. Bottom-hole payment                        A cash payment to the equity participants in a well, on its reaching target depth, by other parties interested in acquiring the information it yields. Bottom-hole pressure Formation pressures measured at reservoir depth. Bottom-hole pump                         (also downhole pump) A pump installed in the lower end of the wellbore, to increase productivity. Bottom of the barrel See Fuel Oil, Heavy Ends etc. Bottoms Up Circulation of drilling fluid in a well, until the bottom hole mud and cuttings reach the surface, indicating that normal circulation can commence. Booster station A platform on a section of subsea gas pipeline, designed to boost the flow of gas. Bow Thruster A propeller mounted transversely in the bows of a vessel to assist in docking, manoeuvring and station-keeping. Box The hollow, or female end in a threaded connection, such as drillpipe. Bridge Plug A down hole packer assembly used in a well to seal off or isolate a particular formation for testing, acidizing, cementing, etc. Also a type of plug used to seal off a well temporarily while the wellhead is removed. Brucker    Capsule     A    circular  escape-and-survival "lifeboat" designed to be lowered automatically on a single wire cable after those entering it have sealed the hatches from within. Bubble Point                       The pressure at which a saturated hydrocarbon liquid releases gas out of solution. See also Absorption. Bullets Cigar-shaped tanks, usually for the bulk storage of propane or butane LPG's as liquids under pressure. Bumper Sub A telescopic joint inserted at the upper end of the string of drillpipe in floating drilling operations, to compensate for vertical motion of the rig with reference to the wellhead on the seabed. Bund Walls The dam or dyke walls surrounding storage tanks or e.g. onshore well installations, to contain the contents in case of rupture or spillage. Bunker ‘C’ A heavy residual fuel oil obtained as a result of distillation of crude oil, and used as fuel primarily for marine steam generation. Bureau Veritas See Certification. Burial History See Maturity. Bury Barge A vessel used to bury completed submarine pipelines in the seabed. This is done by scouring away the seabed under the line with high-pressure water jets, usually mounted on an underwater vehicle known as a tury sled" or "jet sled". The pipeline settles into the trench so formed and is covered by resettlement of the seabed sediment. Breakdown Analysis Captures the project's sensitivity to changes in price, discount rate, RFSU, capex and opex to the point where the NPV becomes negative. The results are best displayed in a tornado diagram. Brent blend   A blend of North Sea crudes, used as an international marker for crude oil pricing. British thermal unit (BTU)         The amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. BTX Abbreviation of the aromatic hydrocarbons, benzene, toluene and xylene. Bulk cargo Any liquid or solid cargo loaded on to a vessel without packaging (e.g. oil or grain). Bunker fuel Any diesel or fuel oil supplied to fuel a ship's engines; i.e. to run the ship rather than as cargo to be transported for sale. The 'bunkers' are the place where it is stored on the ship. Butane A hydrocarbon consisting of four carbon atoms and ten hydrogen atoms. Normally a gas, but easily liquefied for transport and storage; used in gasolines, and for cooking and heating. See also: LPG. Blow-out Preventer (B.O.P.)  is a stacked series of hydraulically controlled safety valves.  When activated the valves prevent the flow of formation fluids to the drill rig in the event of a pressure anomaly being drilled. C Cabletool  Equipment for drilling a well by the outdated cable method. Specifically, the heavy sharpened bar or "bit" which penetrates by being repeatedly dropped in the borehole on the end of the cable. Caliper A tool for checking casing in a well for deformation before e.g. running drilling tools, which might become stuck, or packers which might leak. See Section 5: BGT. Calorific Value     The quantity of heat produced by complete combustion of unit weight of a material. Expressed as either calories per gram, or British Thermal Units (BTU) per pound, or BTU per standard cubic foot of gas. Capbead See Bead. Cap Rock                            An impermeable layer of rock above a discovered or potential hydrocarbon reservoir, providing a seal to contain the reservoir fluids. Carbon                    A solid element which exists in many forms, including diamonds, graphite, coke and charcoal. The combinations of carbon with hydrogen are known as hydrocarbons and can consist of very large molecules (e.g. polypropylenes) or very short ones (e.g. methane). Carbonate rock                          is a sedimentary rock primarily composed of calcium carbonate (limestone) or calcium magnesium carbonate (dolomite), sometimes found as petroleum reservoirs. Carbon black A carbon product obtained from liquified carbon feedstock and used mainly in the rubber industry (e.g. in tyres). Carbon Black Carbon derived from petroleum in soot-like form. Carbon Dioxide (CO2) Injection                         A method used in secondary recovery from an oil reservoir, in conjunction with waterflooding. Carried Interest                      A commercial arrangement, whereby expenditures due from one participant in a joint venture are met by another, usually in exchange for increased equity or repayment out of production revenues. Casing Etc. The steel pipes with which a well is lined, for protection against collapse of the borehole, and unwanted leakage into or from rock formations, or at the surface. "Joints" of casing are around 33ft/10m long and are normally screwed together as they are run into the well. Particularly in offshore drilling it is normal to set large diameter casing, (such as 20") called the Conductor (or surface) Pipe after the well has penetrated the layers nearest the surface, and cement it into place, after which the drilling continues with a smaller diameter bit, etc NB The next string of casing, the "Surface String" is cemented inside the previous string and down to the new Casing Point (see below) which may be at, say 1,000/1,500m and forms the base for the wellhead. This is followed by one or more intermediate strings depending on the target depth and expected conditions in the well. Finally the Inner Production String is set and cemented through the reservoir zone, and perforated to allow hydrocarbons to enter the well. Casing Hanger The lug or bracket from which a string of casing is suspended at the upper end. Casing Head The flanged top of the casing at the surface to which the Blowout Preventer is bolted, and, in production, the wellhead. Casing Point The depth of the lower end of a string of casing. Casing Shoe A reinforced section of casing run into a well at the lower end of a string, to protect against buckling or deformation. Casing perforation   To complete an oil well the casing is perforated in the oil-bearing formation in order to allow the oil to flow into the well.  This operation is performed by a tool made up of a number of linked explosive charges. Casing Tong A large mechanical wrench for screwing or unscrewing casing joints. (Now usually power-operated). Catalyst A substance which aids or promotes a chemical reaction without forming part of the final product. It enables the reaction to take place faster or at a lower temperature, and remains unchanged at the end of the reaction. In industrial processes, nevertheless, the catalyst       must be changed periodically to maintain economic production. Cat Cracker See Cracker. Catenary          The curve assumed by a chain or cable suspended between two points (e.g. an anchor-chain). Cat Head The drum of a power winch accessible from a rig floor or ship's deck for hoisting, pulling and tightening operations. Cathodic protection     A method employed to minimise the rate of electrochemical corrosion of structures such as oil drilling and production platforms, pipelines and storage tanks. Catwalk     A narrow elevated platform or walkway for access to equipment Cave-in Collapse of part of the wall of a borehole usually in a poorly consolidated rock formation. Cavern Storage      Underground natural or man-made storage   chambers  in    suitable  impermeable  or artificially lined rock formations. They may also be designed for cryogenic storage. See also Jug. Cellar Deck   1. The deck or floor beneath the working floor of a drilling rig. The deck below the main superstructure of an offshore platform. Cement etc Cement is used to "set" casing in the well bore and seal off unproductive formations and apertures. It is also used as a coating to add weight to submarine pipelines, which might otherwise float or be easily displaced, particularly when filled with gas. Cement Bond Log (CBL) The measurement made by a tool run in a well to measure the extent to which the cement has bonded with the adjacent surfaces and provided an effective seal. See Section 5. Cement Slurry -See Slurry. Cement Squeeze      in a well is the injection of cement under pressure between casing and borehole wall, especially where bonding is poor, to fill any cavities and to infiltrate the rock to further seal it off. Centipoise (CP) An unit of measurement of viscosity. It expresses the force needed to overcome resistance to flow, and to maintain unit velocity of flow, in a given field. Centralizers Spacing collars attached to the outside of casing when run in a well, to keep it central in the bore and ensure an evenly-shaped annulus in which cement can circulate and set. Centrifuge    A separator operating on the principle of differential acceleration of particles of different mass, an effect produced by equipment similar to a turbine "spinning" the feedstock in an enclosed chamber. Certification (Classification) The process of certifying the origin, quality, and fitness for use or operation to given standards of a platform structure, process, item of equipment etc. It originated in ship construction and insurance  classification. Hence  major  certification authorities acceptable to Government agencies etc., are Lloyds, American Bureau of Shipping, Bureau Veritas and Det Norske Veritas. Cetane Number A measure of the performance of diesel fuel in working conditions (i.e. under compression), similar to the Octane number used for gasolines. CF/D cubic feet per day. Chain Tong A power wrench for tubular connections in which the pipe is gripped and rotated by an endless chain- belt running on rollers. Channeling During production from a reservoir which is being supported by pressure from contiguous water or gas, the water or gas tends to travel towards the. well bore faster through channels or layers of more permeable rock (see Permeability) by-passing and "holding back" production from the less permeable rocks. Check Valve A non-return valve, allowing only one-way flow. Checkerboard leasing A phrase used in exploration to describe granting concessions or leases on alternate blocks. A discovery will tend to increase the value of contiguous blocks still unlet. Choke is a steel nipple inserted into the oil production pipe to restrict the flow of oil from a well.  These nipples come in varying sizes, and often more than one is inserted in the production pipe. CHP                    (Combined Heat and Power) Applied to power generation this refers to the generation of electricity and steam (or heat) simultaneously from the same single fuel, generally to satisfy all the needs of the commercial or industrial site for which it has been designed. In circumstances where process heat is not required, the generated steam can be used to generate additional electricity in a steam turbine; this is described as Combined Cycle Power Generation. Christmas Tree                            The manifold, or arrangement of pipework connections and valves which is installed on the wellhead prior to production. As well as outlets for production, the tree will provide for the injection of mud to "kill" the well, and for the insertion of downhole maintenance tools. Circulation (drilling) The passage of fluids, primarily drilling mud, down the interior of the drill-stem and back to surface via the annulus. Reverse Circulation is in the opposite direction. City gate This refers to the point where gas passes from a main transmission system to a local distribution system. There is not necessarily a change of ownership. CIF cost, insurance and freight. Circulation Bottoms-up -see Bottoms-up. Clastic Rock                       Rock which has been formed from the sediment and detritus of other rocks e.g. sandstone, shale, conglomerates, etc. Clean Cargo  1. Any "white" oils such as gasolines, naphtha, or middle distillates, from the 1ighter end of the barrel" i.e. excluding black oils. Oil with less than 1 per cent basic sediment and water (e.g. for pipeline shipment). Closure Four-way (all round) closure or seal is necessary, over the top and down the gradients on the sides of a potential reservoir, before it can trap or retain hydrocarbons. Closure may be structural as in an anticline, or may be partly due to an impermeable fault, or stratigraphic trapping or e.g. salt intrusion. Cloud Point                     The temperature at which paraffin waxes will solidify and give a cloudy appearance to the oil of which they form part. CO Carbon Monoxide CO2  Carbon dioxide.       Coal gas  Manufactured gas made by the destructive distillation of bituminous coal. The chief components are methane (20% to 30%) and hydrogen (about 50%). Coal Gasification    Conversion of coal into methane, still at the pilot-plant stage. Conversion in the coal-seam by downhole process is also under study. Coating (Pipeline) 1. Cement applied externally, weight- coating. 2. Anti-corrosion compounds applied internally. Cofferdam In platform construction, the "floatable" wall used to seal a dry construction dock. When the dock is filled with water for platform float-out, the cofferdam is de-ballasted and floated to one side to allow egress. Cofferdams have various other uses. Coke (Petroleum Coke)     Carbon extracted from crude oil, usually as result of thermal cracking. It is much like ordinary coke in appearance, but its purity makes it preferable in several industrial processes such as aluminium smelting. Coking   A thermal cracking process to break up large molecules into smaller ones with the generation of quantities of petroleum coke. Combined carrier     Ship that can carry oil or dry bulk cargoes. Combined-cycle gas turbine (CCGT) the generation of electric power by a combination of a gas-turbine cycle and a steam-turbine cycle. Combined heat and power (CHP) The combination of heat and power generation in the same plant. This method reduces the overall consumption of fuel by exploiting the otherwise wasted heat from conventional electricity generation. It provides low-grade heating for domestic and industrial uses. Commercial Well A well capable of producing profitably. Commisioning    Preparatory work, servicing etc. usually on newly-installed equipment, and all testing prior to full production testing (see Start up). Common Carrier       The legal status of some pipeline companies, primarily in the U.S.A. Common carriage     1) The transport of gas through a pipeline system on behalf of a third party. 2) The obligation on transmission or distribution companies to allocate gas transport to customers on a pro rata basis, without discrimination between new and existing clients. Completion 1. Installation in a well of production tubing and equipment, wellhead and Christmas Tree. Fulfilment of a contractual obligation. Completion Test  The procedure specified in e.g. a construction contract, or project financing agreement, for determining whether the plant, field development, etc. in question meets the operating specifications laid down. A completion test may in some cases extend over several months. Compliant Platform Structure A platform capable of "swaying" to absorb sea forces. See also Articulated Platform. Compound Chemical term referring to a substance made up of two or more elements chemically united in fixed proportions by weight. Compressor station Used during the transportation of gas. Gas loses pressure as it travels long distances: to ensure an even flow it must be recompressed at the stations located every 60 km to 80 km along the route. CONCAWE The Oil Companies European Organisation for Environmental and Health Protection, based in the Hague. Concession A defined licence area granted to a company for the exploration of oil and/or gas under specified terms and conditions and for a fixed period of time. Concrete Platform See Gravity Structure. Condensate a light oil which condenses from natural gas when it encounters normal atmospheric conditions. It is a high value refinery feedstock, rich in gasoline compounds and other fractions at the light end of the crude oil range (high API). It is usually colourless. This can refer to any mixture of relatively light hydrocarbons which remain liquid at normal temperature and pressure. There will be some propane and butane dissolved in it. Unlike crude oil, there is little or none of the heavy hydrocarbons which constitute heavy fuel oil. There are three main sources of condensate: •a) The liquid hydrocarbons which are separated out when raw gas is treated. This condensate typically consists of C5 to C8. •b) The liquid hydrocarbons which are recovered at the surface from non-associated gas. •c) The liquid hydrocarbons which are produced from gas/condensate reservoir. Conductor Pipe                         On land and in offshore jack-up or platform drilling, this is driven rather than drilled in to the soil/seabed. In a floating drilling operation, the conductor extends from the rig down to the wellhead on the seabed. Conductor pipe provides a guide and access to the well, and seals off the surrounding sea e.g. to enable circulation of drilling fluid. Confirmation Well An early Appraisal or Step-out well. Coning If an oil well is produced at excessive rates the reduction in reservoir pressure may tend to draw up underlying water towards the well in a cone like shape. Likewise gas can be drawn downwards from an overlying gas cap. Connate Water The original water content of a reservoir rock. Connate water reduces the pore-space (porosity) available to hydrocarbons. Sometimes called Interstitial Water. Consortium A Joint-Venture enterprise used by the oil industry as a vehicle for joint operations where a distinct local legal entity and e.g. joint staffing are required. It may have the legal status of a partnership, limited partnership, joint-stock or joint-guarantee corporation etc. according to local law distinguishable from a light stabilised crude oil.           Constant Value Money (CVM)   The same as Real Terms money. Consumer Price Index (CPI)                       A price index number applicable to a basket of “typical” consumer goods and services Contingent                         Ideas      Ideas    which   depend   on implementation of other (enabling) ideas first. Contaminated Blast                      In a tanker, ballast water which has become mixed with oil. Continental Shelf The shelving area covered by shallow water around major land masses. It may be 50-100 miles/80-200 km in width and merges into the steeper Continental Slope, and yet steeper Continental Rise which descends to the ocean floor. Contract Depth The depth to which a well is to be drilled under e.g. a turnkey drilling contract. Core/Core barrel A vertical section of reservoir or other rock taken in drilling a well, for detailed study and analysis. In order to retrieve the core as intact as possible, it is cut from the rock by an annular core bit The central column of rock passes through the centre of the bit and, as the bit cuts deeper, is received by a hollow cylindrical Core Barrel above the bit, where it is retained and       protected by a series of rubber baffles. When the bit has cut deep enough to fill the core barrel, it is withdrawn from the hole and the core extracted. In this way the actual sequence of rock strata is preserved. Cracker     A refinery plant or process which uses heat (Thermal Cracker) and/or the presence of a catalyst (Catalytic Crack under pressure to break down long- chain-molecule, "heavy fraction" distillates, into more complex and reactive hydrocarbons such as gasolines. See also Reforming. Cracking The process of breaking down large molecules of oil into smaller ones. When this process is achieved by the application of heat only, it is known as thermal cracking. If a catalyst is used as well it is known as catalytic (cat.) cracking. It is known as hydrocracking if the catalytic process is conducted in a hydrogen atmosphere. Creaming Curve   An expression reflecting the fact that the largest reservoirs in a prospective petroleum province tend to be found first, followed by a predictable progressive decrease in the size of discoveries. Critical Path Analysis A project planning tool normally used in large construction development projects. It is based on a "network" of necessary actions of known sequence and duration, and aims at identifying priority points at which actions ,"critical to" (holding up other progress on) the project need improvement or elimination. Critical pressure  The minimum pressure required to liquefy a gas at its critical temperature. Critical temperature     The temperature above which a gas cannot be liquefied whatever the pressure. Crown Block The upper fixed pulley assembly at the top of a drilling derrick. Crude assay is a procedure for determining the general distillation and quality characteristics of crude oil. Crude Oil An unrefined mixture of naturally-occurring hydrocarbons. Because it is essentially a mixture, the density and properties of Crude Oil vary widely. Light Crude normally has an A.P.l. gravity of 300 or more. Gravities of 200 to 300 include the medium gravity Crudes, while those below 200 are known as Heavy. Heavy Oils are found right down to the residual solid state. See Section 8. Sour crude has a significant sulphur content: Low-sulphur crude is described as Sweet. Cryogenics/cryogenic storage         In oil industry terms this refers to very low temperature(below -46€C/-50€F) handling  processing  or   storage  of   hydrocarbon substances. See also Cavern Storage. Cubic foot/feet (cf) The amount of gas required to fill a volume of one cubic foot. Unit of measurement applied to the volume of gas produced or consumed. Cubic Metre (CM) Unit of measurement for gas volume. The amount of gas required to fill the volume of one cubic metre. Cuttings The small chips or flakes of rock retrieved from a well by the circulation of the mud. They are studied and logged by the well-site geologist. Cut/Cut Point     A "cut" is a hydrocarbon substance or group of substances extracted from a wider mixture in a refining process. For instance, primary distillation will usually yield a Naphtha Gasoline cut, a Middle Distillate cut, and a Residual Fuel Oil cut, with an "Overhead Cut of gases. The specific gravity at which each cut is separated by the process is the Cut Point. Cuts are made with   progressive fineness and accuracy as the oil proceeds through the refinery. D Daily average send-out Total volume of gas delivered during a period of time, divided by the total number of days in the period. Daily contracted quantity (DCQ)  The average daily quantity of gas which is contracted to be supplied and taken. Daily peak The maximum volume of gas delivered in any one day during a given period (usually one year). Daisy Chain A name given to a series of interdependent contracts for future purchase and sale of oil. Darcy The unit of measurement of rock permeability, i.e. the extent to which it will allow a fluid to flow through it. The permeability of most oil and gas reservoir rocks is measured in millidarcies, (thousandths of a Darcy). Data                     Although applied to any factual information, this term most commonly refers to seismic "data"-the computer records and output of a seismic survey. Dead Oil Oil containing no naturalgas. Dead Weight Tonnage The load-carrying capacity of a vessel, the "live" weight being the displacement weight of the unladen vessel. Dead Well A well which will no longer produce without further stimulation. Dealkylation A cracking process whose main product is aromatic hydrocarbons. Debutaniser, Depropaniser etc.                             A process vessel (column) set to "cut' or extract a specific hydrocarbon fraction. Decision Hierarchy A tool to prioritise the issues that form the core of any quantitative analysis  Decision Trees                              A logic tree asks critical framing questions, a decision tree quantifies the available options. A decision tree is a step-by-step map of future decision options, the expected spread of outcomes resulting from those decisions and the likelihood or probability of those outcomes actually occurring Decompression/Decompression                             Chamber      The process of gradually reacclimatising deep divers to surface pressure conditions. For relatively shallow dives this is achieved by controlled rate of ascent. For longer, deep, tt saturation" dives, the divers are recovered under pressure into a Decompression Chamber where pressure reduction may take some days. Deep Rig  A drilling rig designed and equipped to withstand the loads and pressures associated with drilling to deep objectives (e.g. over 20,00076,000m). Deep Well                     See Deep Rig. The deepest so far drilled by the industry is approximately 30,00079,000m. Default                     There are many uses of this term, but it is of major importance in Joint Ventures, whereby a participant which fails to meet its cash contribution obligations may in specified circumstances lose rights in the concession in question.       Deficiency Gas In a "Take or Pay" gas sales contract, this is an amount of gas which must be paid for although not taken. De-Gasser         1. A separator which removes from the returned mud flow any entrained gases from formations down the well. Gases can cause a potentially dangerous reduction in the density of the mud and hence its ability to contain down-hole pressures. Any process which removes gases of various kinds from an oil flow. Degree day A measure of the extent to which the mean daily temperature falls below an assumed base, say 65° F. thus each degree by which the mean temperature for any day is less than 65°F would represent one degree day. (In Continental Europe, °C are used instead of °F and the assumed base temperature is generally taken as 16°C, equivalent to 60.8°F). Dehydrator (gas) Equipment for the removal of water from a gas stream, for instance prior to transfer by pipeline. Delineation Well      A name for an appraisal well, usually one drilled specifically to determine the boundary of a discovered reservoir. Demurrage      Originally, charges for keeping shipping waiting outside the times allowed in the freight contract. It mainly relates to oil tankers, but can be applied to any major facility. For instance, Pipeline Demurrage is chargeable for late delivery to or from a pipeline system. Dependencies Contingent ideas - ideas which depend on implementation of other (enabling) ideas first Depositional environment   The conditions under which a series of rock strata were laid down.  Depositional environments are divided into five groups:  marine (ocean- borne), aeolian (wind-borne), alluvial (river- borne), deltaic (borne by a river at its delta), and inter-deltaic (between river deltas). Depletion etc. Progressive reduction in reserves as a result of production. Depletion Allowance in some countries is a type of tax-allowable amortization recognising this reduction. Depletion Drive is primary production, i.e. as a result of expansion of reservoir gases with decreasing pressures. Depth Map      A relief map of a sub-surface geological structure where the contours relate to depths from the surface datum level, (i.e. sea level). This is a further interpretation of a seismic time map. Derrick etc. A pylon-like steel tower which provides the vertical lifting capacity needed for drilling a well. The Derrick Man is the member of the drilling crew who works up within the derrick on the tubing board or "monkey island", a platform where the upper ends of stands of drillpipe or casing are handled, and hung onto or detached from the Kelly or hooks. (See Drilling Rig, and diagram). Derrick barge is a sea-going barge fitted with a larger crane(s) capable of lifting objects of up to 2,000 tons of weight.  Such barges are used extensively in lifting heavy modules on to platforms out at sea. Derv See Diesel fuel Desalter Apparatus for removing salt and salt water from crude oil. Design Wave The maximum size and frequency of wave that an offshore structure must be able to withstand. Deterministic Model The simple cashflow models that represent each strategy option             Development Any major construction such as a refinery,           Distribution After gas has been processed, it is     or a production project. It has come to mean, or cover, the whole life of a production project from design to abandonment. Strictly speaking it refers to the planned, and actual production of reserves from a reservoir. Development Well  Any well drilled in the course of extraction of reservoir hydrocarbons, whether specifically a production well, or injection well, See also Exploitation Well. Deviated Well/Hole                              A well whose path has been deliberately diverted from the vertical. Although relatively costly to drill, they are used particularly offshore to reach distant parts of a reservoir from a single platform. Deviated, or directional drilling up to 60c, to 70c, from the vertical is now fairly common. Greater deviation is possible with special equipment-see Horizontal Drilling and Slant Drilling. Dewpoint The temperature at which liquid condenses from a gas at sea level pressure. Diamond Bit See Bit. Diapir                     An up-thrust intrusion of lower-density rocks through overlying formations, e.g. a salt dome. Diesel fuel (oil)                       A general term covering light fuel oil derived from gas oil used in diesel engines. Sometimes called Diesel Engine Road Vehicle (Derv) fuel. Differential Pressure                           The difference between the pressure in a well due to the mud column and the pressure in the surrounding rock at any point. See also Sticking. Dip, Diameter 1. The inclination from the horizontal of he top surface of a geological structure. A Dip meter indicates dip relative to a well bore. See Section 5, HDT. Measurement of the contents of a tank by lowering a weight and prepared line into it. See Tank Dipping. Directional Drilling See Deviated Well. Dirty Cargo                     Crude oil, or any cargo containing black oil or residual oils. Discounted Profitability Index (DPI) A measure of the NPV generated by a project for every (discounted) dollar of capital spent. Discount Factor Calculates the investment or time-value of money; today's dollar is more valuable than tomorrow’s dollar. Discounting The discounting has the effect of reducing the value of future income in comparison to the cost of early expenditure. It takes into account the risk that the income anticipated in the future is less than that predicted by discounting its value. Discovery Well A successful exploration well, or wildcat The first successful well on a new prospective reservoir structure. Distillates                      The products of condensation during the fractional distillation process (gaseous fuels, naphtha, gasoline, kerosine and gas oils). Distillation/Distillation Column/Distillate The process of heating and "flashing" or boiling off successive fractions (component hydrocarbon substances) from a crude oil feedstock, or a product of earlier distillation. A Distillation Column is an elongated vertical process vessel designed to give optimum physical separation of required fractions "flashed" inside it. The products of distillation are known as Distillates.   transported through transmission trunk lines to local distribution centres, for metered delivery to customers Ditch Cuttings See Cuttings. Originally retrieved from the "ditch" of early land-based mudsystems. Diurnal storage Literally, daily storage. Refers to short- term or peak storage in pipelines or gas holders, as opposed to seasonal storage. Diverter A safety device fitted in the early stages of a well, instead of a blowout preventer, to divert and vent off any shallow gas encountered. Dog-leg         Where a well has been deviated and later returned to vertical. The expression may also be applied to any similar double bend in a pipeline or well. Dog House The Driller's enclosure or shack which serves as a well-site office and control room. Domestic Gas (DomGas)          Natural gas, supplied by pipeline is a mixture of different gases, mostly methane (85% North Rankin). Other components include ethane, propane, butane, pentane, carbon dioxide and nitrogen. It occurs in pressures of 31-49 Mega Pascals in reservoirs on the North West Shelf. Dope A grease-like substance used to protect and seal joint-threads of well tubulars such as casing. Double bottom tanker A tanker in which the bottom of the cargo tanks is separated from the bottom of the ship by a space of up to 2 to 3 metres. The space is empty when the tanker carries cargo, but full of sea water on the ballast voyage. See also: double hull tanker. Double hull tanker     A tanker in which the bottom and sides of the cargo tanks are separated from the bottom and sides of the hull by spaces of up to 1 to 3 metres width or depth. These spaces are empty when the tanker carries cargo but full of sea water on the ballast voyage. See also: double bottom tanker. Down Dip An area of a structure where the top of the formation is lower (e.g. offshore, deeper below sea level) than the point under consideration. Down Hole  Down a well. The expression covers any equipment, measurement, etc., in a well or designed for use in one. Downstream "Downstream" is a relative term (the opposite of "Upstream") in oil industry operations. For instance, a refinery is "downstream" of a crude oil production unit, and a petrochemical plant usually downstream of a refinery. The term has also come to mean all operations occurring after the delivery or lifting of saleable quality crude or gas from the production unit or associated delivery terminal. A "Downstream Company" has no production of its own. Downtime      A    period  when   any   equipment is unserviceable or out of operation for maintenance etc. Drape structures occur when sediments are deposited or draped over the physical relief of older rocks.  Such features can include old fault traps or anticlines. Drawdown The difference between shut in and flowing bottom hole pressures. Drill bit  The part of a drilling tool that actually cuts through the rock. Drill Collar See Drill String. Drill Pipe  Pipe, usually of 3.5 in. to 5 in. outside diameter, which is supplied in "joints" normally of around   33 fL/10 m. in length, each being fitted with thicker, or "up-set"' reinforced threaded couplings at each end, 66 male and female" or "pin and box" respectively. To save time, drill pipe in use but not in the well is stacked in stands. Drill Ship A ship-shape offshore drilling rig for exploration in very deep waters. Although less stable than a semi- submersible rig it has greater load carrying capacity and is therefore more self-contained when far from land. Drill Stem/Drill Stem Test The assembled drill pipe in the well is known as the Drill Stem, and serves three main purposes; to rotate the bit; to convey drilling mud or cement down the well, and to flow to surface the fluids in primary assessment of a discovery, (Drill Stem Testing/DST). See also Drill String. Drill String The assembly of bit (for penetration) drill collars (for weight, rigidity and torque transmission), stabilizers (to ensure straight hole and help transmit torque), and the length of drillpipe in use in the well. Penetration is achieved by "weight on the bit, or the weight of the drill string minus the weight of the equivalent volume of mud in the well. Drilling Crew The crew on a drilling rig is supervised by a senior drilling engineer, known as a "Toolpusher". Other members of the crew ' include the Driller, in charge of a shift, who ensures adherence to the drilling programme and maintenance of the shift's operating log, or 7our Sheet". He controls the lifting mechanism and hence the weight on the bit (see Drill String). Other skilled members, or "Roughnecks" may be Motor men, Derrickmen, Floor men, Pump men, etc. Partly skilled or unskilled members are known as "Roustabouts". In addition a rig crew will incorporate such specialists as Mud Engineers and Well-site Geologists. Drilling Fluid See Mud. Drilling mud                     A mixture of clays, water and chemicals used in drilling operations to lubricate and cool the drill bit, carry drilling wastes to the surface, prevent the walls of the well from collapsing, and to keep the upward flow of oil or gas under control. It is circulated continuously down the drill string and up to the surface between the drill pipe and the wall of the hole. Drilling Out                       When a well must be deviated or side- tracked, either as planned or to avoid a fish it is normally necessary to cut a hole in the casing wall and drill out on the new path. Drilling Report Every twenty-four hours the Driller's log and the geological cuttings log, together with the observations of the Toolpusher and any other significant data, are sent, usually by telex, to the Area Drilling Manager and other interested parties. The report will also include e.g. usage of materials, stock levels, and requirements for supplies. See also Drilling Crew Drilling Rig                        Almost all drilling is now carried out by rotary rigs. A diagram of a typical offshore rig is shown on this page. The "Rig" comprises a derrick, a draw-works or source of power, lifting tackles and blocks, a kelly and rotary table to rotate the drill string, a mud pump and mud circulation system, a blow out preventer, and a system for handling drillpipe, casing etc. Drilling Tools A term applied generally to any down-hole accessory including for instance stabilizers, jars, fishing equipment, and directional drilling apparatus. Drive Pipe See Conductor Pipe.       Dry Gas   Natural gas, methane and ethane, without any significant content of heavier hydrocarbon fractions. Dry gasfield    The production from such a reservoir will yield dry/lean gas and very small quantities of condensate; typically less than 10 barrels per million cubic feet. Dry Hole      An unsuccessful well. Sometimes called a "Duster". Dry-trees   See Sub-sea wellheads Dynamic positioning (DP)          A system of computer- controlled directional thruster propellers which enables a "DP" floating rig or drillship to maintain position over a subsea well without using anchors. It is mainly used in deep water where anchoring would be impractical, but may also be used in the vicinity of vulnerable seabed installations. Dwt (Dead weight tonnage) The weight of cargo, stores and fuel which a vessel carries when fully loaded. E Economic depletion Progressive reduction in the value of a producing asset as a result of production. See also Depletion Allowance. Economic Life           The date when there is no longer sufficient return to justify any future investment Economic Zone The area of the seabed over which an adjacent state can claim rights of exploitation (currently up to 200 miles). ECT Energy Charter Treaty - signed by 45 governments and the EU in Lisbon, Portugal on 17 December 1994. ECU European Currency Unit. Edge water is that water underlying and marginal to oil and/or gas accumulations. Effective permeability   The permeability of a rock to fluid when the saturation of the fluids is less than 100%. Electric Log See Log. Electric Swivel powered swivel which rotates the drill stem from above the rig floor, thus replacing the kelly and rotary table. Electro Drill  A bit powered by an electric down-hole motor which operates without the need to rotate the drill string. Element  A chemical term referring to a substance that cannot be chemically broken down into a simpler form. Elevators A clamp used in a drilling rig to latch on to and grip drillpipe, casing, etc., when lifting the EMULSION Water droplets, each encased in an oil film so that it cannot break free to separate by gravitation. An Emulsion treater normally uses heat to break down this resistance ELSBM  Exposed Location Single Buoy Mooring system is a semi-submersible structure, designed to enable tankers to off load oil directly from an offshore oil field. Emulsion A mixture in which one liquid is dispersed in another in the form of very fine droplets. Enabling Ideas Ideas which are necessary for successful implementation of other ideas               Enhanced recovery is a method(s) applied to depleted reservoirs to increase the overall recovery factor.  After an oil well has reached depletion, a certain amount of oil remains in the reservoir, which enhanced recovery is targeted to produce.  (See secondary recovery and tertiary recovery.) Enhances oil recovery (EOR) Techniques sometimes described as Tertiary Recovery. They include, for example, injection of surfactant or polymer into the reservoir, fireflooding, steam injection, and microbial action. Entrained Oil/Gas Small amounts of oil which may form part of a gas stream, due to the difficulties of separation at source. Similarly gas may be entrained in a stream of other fluids. Environmental                       Impact      Assessment       (EIA)    An assessment of the impact of an industrial installation or activity on the surrounding environment, conducted before work on that activity has commenced. The original baseline study, a key part of this process, describes the original conditions. EOR (Enhanced Oil Recovery) The recovery of oil from a reservoir other than by the use of natural reservoir pressure. This can involve increasing the pressure (secondary recovery) or heating or increasing the pore size of the reservoir (tertiary recovery). See also: acidizing. Equity Crude Crude Oil belonging directly to the equity participant in the oil field, as opposed to 'Tarmer's crude", royalty oil, Government participation crude, etc. Escarpment                           is a cliff or relatively steep slope that separates level or gently sloping areas of land. Esters                    Compounds formed by the combination of acids and alcohols. Feedstock for the chemical industry. Estimated Date Money                       “What it cost at the estimate date” – the money type for cost estimates but sometimes requiring adjustment to the Reference Date. Ethane                    A hydrocarbon consisting of two carbon atoms and six hydrogen atoms. Normally a gas, present in most natural gas occurrences. Ethanol (ethyl alcohol)                            A chemical formed by fermentation or synthesis; used as a raw material in a wide range of industrial and chemical processes. Ethylene (ethene) An olefine consisting of two carbon atoms and four hydrogen atoms; a very important base chemical in the chemical and plastics industries. EU European Union. Expansion Loop A bend or loop installed in a length of pipeline to absorb longitudinal expansion with changes in outside temperature, the passage of hot oils, etc. Expected Monetary Value (EMV)                      The risked NPV or the probability of achieving the project NPV (NPV * Probability of occurrence). A positive EMV indicates acceptance of the proposal, a negative EMV indicates rejection. The higher the EMV, the higher value ranking of the project. Exploitation Well A development well, e.g. an oil or gas producer, or gas or water injector to support production. Exploration/Exploration Well                              Exploration is the process of identifying a prospective hydrocarbon region and structure, mainly by reference to regional, and specific, geochemical, geological and geophysical (seismic) surveys. An Exploration Well is a well drilled to test a potential but unproven hydrocarbon trap or structure       where good reservoir rock and a seal or closure combine with a potential source of hydrocarbons. Exposure (or cash sink) The maximum value of the cumulative RT cash deficit ( in financial reports usually in MOD). "EXPRO" Exploration and Production. (Colloquial). F Facies        In geology, the "appearance" and hence the composition and characteristics of a rock formation. Cores are taken from a well, for example, so that the reservoir facies can be studied. A Facies Trap for hydrocarbons is one in which the seal or closure is provided by a change in rock characteristics, a form of stratigraphic trap. Farmers Crude Landowner's royalty-in-kind. Farmin /Farmout In a normal farm-in a company acquires equity rights to a concession by drilling a well at its own cost for the benefit of the company or companies "farming-out". For example, it may drill one well to a stated depth for a 25 per cent equity in the licence. Fat Oil/Lean Oil Saturated or under-saturated oil. "Fat" Oil could, for example, be saturated with gasolines absorbed from a gas stream in a refinery. The oil is "lean" when the gasolines have been distilled out again, and the oil recycled to the process. See also Lean Gas. Fault/fault Block      A discontinuity in a rock formation caused by fracturing of the earth's crust. There are various causes of fault-fractures such as the movement of 1ectonic plates" relative to each other. In oilfield terms a Fault Block is a compartment of a rock formation surrounded or partly surrounded by faults, which may have sealed in hydrocarbons separately from the rest of the formation. Faulting A geological structure consisting of a fracture in the rock, along which there has been an observable amount of displacement Fault traps are caused when a reservoir layer such as sandstone is faulted and brought against an impervious rock enabling any oil or gas to collect against the fault. Field        See Oilfield. A field may also be a gas or gas condensate field. Feedstock Raw material for a processing unit. FERC   Federal Energy Regulatory Commission: the government organisation in the US whose responsibilities include regulating the gas industry. Field appraisal  The process of quantifying reserves levels and production potential of a newly-discovered petroleum reservoir, usually by drilling a delineation well. Filter Cake/Filtrate Build up of mud solids or filtrate on the wall of a well. This helps seal and stabilize the rock face, but too much can cause sticking of the drill string. See also Differential Pressure. Fines Small particles of rock or other solid. Fingering Uneven advance of water and/or gas towards an oil well due to inconsistent permeability in the   reservoir. When the finger reaches the well oil will tend to be excluded. Finger Boards These comprise a rack for the upper ends of stands of drillpipe. Finger Pier A jetty at right-angles to the shoreline, so that tankers can moor to load and unload in deep water. Finger printing                     Crude oil is a mixture of hydrocarbon components or fractions and other minerals. The composition of each crude is different in consequence, leading to differences in gravity, etc. Nowadays, the source of a crude - e.g. an oil-spill - can be determined by analysis known as "finger printing". Fireflooding A form of Enhanced Oil Recovery in which otherwise unproduceable heavy oils are ignited in the reservoir. The cracking effect enables resulting lighter fractions to be recovered. Fiscal Costs  The deductions allowed against revenue when calculating tax – generally royalty, operating expenses and depreciation. Fish/Fishing                       Any unwanted object down a well, commonly the lower end of a drill string which has broken off. "Fishing" is trying to recover the Fish, using various attachments to the drill stem or wireline, known as fishing tools. Five Spot Water Flood                             A standard method of development where a production well is surrounded by four water injection wells to "sweep" the maximum amount of oil towards the producer. Fixed Bed Catalyst/Fluid Catalyst                           Catalyst which remains in place in the reactor vessel rather than being pumped in with the feedstock as with Fluid Catalyst. Flame Jet Drilling                       The use of a rocket-fuel flame to penetrate rock by fusing (melting) it. The flame also glazes and seals the walls of the well with fused rock. Flange Up                      To connect; to complete; to put into operation. Flare/Flare Stack                          A vent for burning off unwanted gases or to burn off hydrocarbons which due to temporary malfunction or maintenance of process plant, cannot be safely stored or retained in process vessels. A Flare Stack is the tower from the top of which the burn-off can safely take place. Flash Off  To vaporize or "boil off" a hydrocarbon by heating. Flash Point The lowest temperature at which a vapour will burn or explode when ignited. Flotation collar   This is a specially designed raft, which   enables steel jacket platforms to be transported from the place of construction to the oil field in a horizontal position.  When over the proposed offshore location of the platform, the collars buoyancy compartments are flooded thereby allowing the platform to swing to a vertical position.  When the platform has been placed on the seabed and secured by piles, the flotation collar is detached and taken back to the shore. Float/Floating Casing                         A method of inserting heavy lengths of casing into a well without overstressing joints and seals due to the weight of the total string. The bottom end is sealed, and the hollow string then becomes buoyant in the drilling fluids in the well, which are gradually displaced. Afterwards the seal is drilled out and the casing cemented into place. Floating Production Facility (FPF) A vessel designed to provide offshore field production control and processing for smaller fields, more cheaply man a fixed platform. The tension-leg platform is specifically designed to meet this need in deeper waters but transport barges, semi- submersible drilling n . gs, and tankers are all capable of modification for the purpose depending on water depth Floating Roof Tank Crude oils (and some Other oils) are normally stored onshore in tanks whose roofs float on, and in contact with, the oil, avoiding a cavity in which volatile and dangerous gases could build up. Float Out/Floatation/ Floatation Can       The launch or loading out of jackets or other structures for installation offshore, on a Flotation barge or other vessel, or in some cases usirM their own buoyancy. Flotation Cans are hollow tanks attached to a jacket to assist buoyancy or help control the lowering to the seabed. Flood    To let or pump water into ballast tanks. See also Waterflood and Fireflood. Flotel The floating accommodation used as quarters for offshore personnel Flowing Bottom Hole Pressure   Bottom hole pressure measured at a given flow rate. Flowline Bundle An integrated assembly of production pipelines, and hydraulic and/or electrical control lines, connecting a Subsea satellite well to its parent installation. Flowmeter/Flow chart A meter to measure the rate at which a fluid passes a given point. A Flow Chart or flow graph provides a permanent graphic record usually over a 24 hour period. Fluid Cat/Cracking See Catalytic Cracker Flush Phase         The primary production p h as e of a reservoir. Foam Blanket A fire protection device. Inert gas foam is floated on the surface of liquid hydrocarbons in storage to exclude contact with air and evaporation of combustible gases. Foam Blankets are also used in fighting hydrocarbon fires. FOB free on board. Fold is  a flexure of rock strata into arches and troughs, produced by earth movements. Footage/Footage rate           Penetration rate in drilling. Footage Rate may also be a form of remuneration under a drilling contract. Often referred to as ROP (Rate Of Penetration). Footprint   The limit of radius of action of an  underwater vessel or vehicle. The impact/impression on the seabed of a 1 . ack-up facility. Force Field A list of major issues - for and against the proposal Formation A rock deposit or structure of homogeneous origin and appearance. Formation Damage         Damage to the reservoir rock around a well due to e.g. plugging with mud, infiltration by water from the well, crumbling under pressure or high flow rate, etc. Fractional distillation See Distillation. Fractionating column See Distillation. Fractionation    The general name for the process of separating a mixture into its constituents or fractions. See also: absorption, adsorption, distillation.  Formation Density Log See Log. Fraction/Fractionator                          A hydrocarbon substance of specific molecular composition, or closely related group of such substances, extracted from a crude oil or natural gas stream, predominantly by distillation in a Fractionating Tower or Fractionator. Fracturing                     The process of cracking open the rock formation around a well bore to increase productivity. This is normally done by applying hydraulic pressure down the well bore. Fraction/Fractionator Gas Chromatography A hydrocarbon substance of specific molecular A very accurate laboratory method of separating composition, or closely related group of such and analysing the components of a volatile substances, extracted from a crude oil or natural hydrocarbon mixture. Free Cash Flow                       The cash flow used in determining a projects NPV and IRR. It is the total after-tax cash flow generated by a project and available to all providers of capital. It is essential to define free cash flow properly to ensure consistency between the cash flow and the discount rate used to value the project. FSU (Floating Storage Unit) A large moored chamber in which oil produced from an offshore production platform is stored before being transferred to a tanker. See also: SBM (Single Buoy Mooring). Fuel cell                         An electric cell used to generate electrical energy from the reaction of a number of chemicals, without the need for combustion and without producing noise or pollution. Can use natural gas as a feed-stock. Fuel gas                         Refers to gaseous fuels, capable of being distributed by pipeline, such as natural gas, liquefied petroleum gas, coal gas and refinery gas. Fuel oils The heavy oils from the refining process; used as fuel for power stations, industry, ships etc. Futures (oil). The sale and purchase of oil at a price agreed upon in advance for delivery at a future date. The seller may not yet have the oil and both buyer and seller are speculating on how prices will change in the future. G Gamma Ray Log/Gamma Gamma Log See Log. Gang Pusher Supervisor of a pipe laying crew. Gas Cap/Gas cap Drive The natural accumulation of associated gas in the top of an oil reservoir. Gas Cap Drive, or primary production utilizes the pressure and expansion of this gas to drive the oil to the surface. Sometimes called Depletion Drive. Gas Column See Oil Column/Gas Column. Gas Condensate                     Light hydrocarbon fractions entrained in gas production which condense into liquid when brought to the surface. Changes in reservoir pressures as result of production may cause it to condense in the reservoir, when much of it may become irrecoverable. See Retrograde Condensation.       Gas/condensate field A reservoir containing both natural gas and oil, with a greater proportion of gas. Condensate appears when the gas is drawn from the well, and its temperature and pressure change sufficiently for some of it to become liquid petroleum. Gas/condensate ratio         •a) For a gas/condensate reservoir this is the ratio of the condensate to the gas. As for oil it can be measured in scf per bbl. Alternatively the inverse is used and the typical units are bbl per mmscf. b) For a dry gas field only the inverse is normally used. Typical units are again bbl per mmscf, but grammes per cubic metre may well be used. Gas/condensate reservoir A reservoir in which neither natural gas nor crude oil is the predominant production stream. To increase the recovery of the condensate, the gas may be re-cycled for the early years and produced at a later date. Gas cycling or re-cycling A process in which produced gas is re-injected into the reservoir after removal of the condensate. This is to maintain the reservoir pressure and prevent condensate from "condensing" in the reservoir and then becoming difficult to recover. This is called retrograde condensation. Gas detector An instrument to detect the presence of various gases, often as a safety precaution to guard against flammable or toxic gases. Gasfield A field or group of reservoirs of hydrocarbons, containing natural gas, but insignificant quantities of oil. Gas gathering system  A central collection point for offshore gasfields, with pipelines from a number of fields, often owned by a number of different companies. From there, the gas is transported to a central processing system onshore. Gas grid     The term used for the network of gas transmission and distribution pipelines in a region or country, through which gas is transported to industrial, commercial and domestic users. Gas Injection    A secondary recovery method by which gas is injected into and passed through the reservoir to maintain pressure and/or entrain heavier hydrocarbons left behind by primary production. The reservoir can in this way also serve as storage for produced gas until the reservoir pressure can be reduced, and the gas sold. Gas Kick    Increase of down hole pressure above that exerted by the column of drilling fluid in a well, allowing gas to escape to the surface. If not controlled this could develop into a Blowout. Gas lift  One of several methods of artificial lift. A mechanical process using the continuous or intermittent injection of a gas into the production conduit (tubing or casing) to aerate or displace the produced fluids. This creates a reduction of the bottom hole pressure of the well, increasing or sustaining the flow rate of the well. Gas liquefaction The process of cooling natural gas to a temperature of -162°C, thereby reducing its volume by a factor of 600, and making it liquid. The resulting LNG is then transportable by purpose-designed ships (LNG carriers) or may be stored in tanks Gasohol     A motor fuel which includes a proportion of plant alcohol processed from vegetable waste. Gas Oil A middle distillate product fraction. See Sections 8 and 11.  Gas/Oil ratio (GOR) The proportional amount of gas to oil liquid occuring in production from a reservoir, usually expressed as cubic feet per barrel. Gas processing The separation of oil and gas, and the removal of impurities and natural gas liquids from natural gas Gasser A gas well. Gas treatment                       Removal of impurities, condensate, hydrogen sulphide and any liquids from the raw natural gas contained in a gasfield. Gas turbine A turbine propelled by the combustion of a compressed mixture of natural gas and air, used for power generation. Gas oil The medium oil from the refining process; used as a fuel in diesel engines, burned in central heating systems and as a feedstock for the chemical industry.  Gasification The production of gaseous fuel from solid or  liquid fuel. Gas/oil contact   The interface between the gas cap on a reservoir and the underlying oil leg. Gas/oil ratio (GOR)   This is the proportion of associated gas produced with the oil and is usually expressed in standard cubic feet or gas per barrel of oil (SCF/BBL). The higher the ratio the more separation facilities are required so that the gas can be transported to shore separately, flared or re-injected into the reservoir. Gasoline The fuel used in cars and motorcycles etc (also known as petrol). Naturally occurring gasoline is known as condensate. Gas well  A borehole sunk into the ground with the objective of bringing natural gas to the surface. Gate A pipeline valve. Gatt The General Agreement on Tariffs and Trade. Gauge pressure The pressure which a normal measuring device would register. Such devices measure the pressure which is in excess of the atmospheric pressure. Geared Project                       Project that is (partly) financed with outside loans. Geochemical Survey Analysis of the hydrocarbon- bearing potential of an area by studying shallow cores and subsurface water for evidence of seepage or kerogens. Geology/Geologist The study of the history of the earth and its rocks. The geologists in the oil and gas industry tend to specialise in Sedimentoiogy, Palaeontology and other branches of the science relating directly to prospectivity for hydrocarbon deposits. Geological Column/Geological Eras/Ages                         This is a name given to the vertical succession of geological deposits from successive eras, found in any specific place. These columns vary considerably, but a general reference sequence is shown in Section 3. Chiefly of interest to oil and gas geologists are those showing evidence of life- forms deposited long enough ago to have generated hydrocarbons. Geophones                     Sound wave receivers primarily for onshore seismic surveys. See also Hydrophone. Geosyncline See Syncline. Geophysics/Geophysicist                         Physics applied to the measurement of the earth and study of its composition. A Geophysicist NOTES in the oil and gas industry usually specialises in the interpretation of seismic survey data.  Geothermal energy  Energy obtained from the heat below the Earth's surface. Geothermal gradient The increase of temperature with depth in the earth's crust. (About 211F. per 100 feet). Gigawatt Thousand megawatts. Gin Pole A frame used as a vertical support for hoisting. The highest point of a drilling derrick is usually the gin pole for working on the crown block. GJ Gigajoule: equivalent to one billion (109) joules. Gooseneck The curved connecting pipe or nipple on the drilling swivel, to which the rotary hose from the standpipe is attached. Graben           A structure which has become displaced downward from its original surrounding geological setting.  Grass Roots   Description of a refinery or other  development project where there is no existing plant or infrastructure-i.e. construction on a "green field" site. Gravel Pack Where the producing formation in a well is crumbling or caving into the well bore and plugging the perforations, the cavity so formed is filled with fine gravel, which supports the formation, and keeps the interior of the well clean. Gravimeter        An instrument which measures minute variations in the earth's gravitational pull at different surface points due to the density of the underlying rocks. A gravimetric survey uses this principle in the search for sedimentary rocks which normally have a relatively low density. Gravimetric survey   Rocks have different densities and lie at different depths causing slight variations in the force of gravity at the surface.  These are measured by gravimeters and enable the geophysicist to collect information on the shape and nature of the underlying rock. Gravitometer An instrument which measures differences in the specific gravity of liquids, and is used to identify interfaces between batches of different products in a pipeline. Gravity Platform Structure  Offshore platforms etc., which rely on weight alone to keep them stable and in place. They are frequently made of concrete with steel as a major component. Steel gravity structures are also used. Structures of such size are floated into position, the buoyancy being provided by hollow chambers in the large base of the platform. Subsequently these are flooded with water, and can be used for oil storage. Greenfield Often used to refer to a planned LNG facility which must be built from scratch; without existing infrastructure. Groupshoot A seismic survey shared by several sponsors Grout/Grouting    Concrete filling the cavity around e.g. steel piles of an offshore platform, as a result of a cementing operation similar to setting casing. Guide Bas/Lines/Posts          The seabed framework or template through which a subsea well is drilled. It is fitted with Guide Posts from which Guide Lines extend to the surface, and enable the wellhead to be located ready for drilling, and for installation and control of e.g. the Blowout Preventer. Gumbo A sticky, clogging mud formed in some wells by the mixture of drilling fluid with certain types of shale.  Gunk                    The accumulation of rubbish, rust, detritus and petroleum deposits that accumulates in a pipeline until it is pigged. Gun 1. See Perforation. 2. A source of sound for seismic surveys. Gusher                    An old name for a successful well with a high pressure leading to a blowout Now uncommon. H Hanger See Casing and Tubing. Hanging-in the Casing                      Tensioning a string of casing while cementing by letting it hang from the wellhead. This helps to offset later expansion due to the passage of hot fluids. Hanging in the slips Suspending drill string or casing from slips or wedges placed in the rotary table. Hazard Zone                     An area where special safety precautions apply. Heading Intermittent flow of oil from a well, usually from lack of reservoir gas pressure. Heavy fractions Also known as heavy ends, these are the oils made up of the large molecules that emerge from the bottom part of the fractionating column during oil refining. Heat exchanger A process vessel which typically uses the passage of one fluid through a set of internal tubes to heat up or cool down another fluid in which they are immersed. There are many different designs and uses. Heat Tracing See Tracing. Heave/Heave Compensator                       The vertical motion of a floating vessel or platform with the waves. A Heave Compensator is installed on floating drilling rigs to counteract this movement as regards the drillstring and marine conductor. Heavy Ends Heavy or residual fractions of a feedstock after distillation, etc. Sometimes referred to as the "bottom" or "heavy end" of the barrel. Helipad                     A Helicopter landing deck or onshore landing area. High (Geological)                         The part or parts of a geological structure which are nearer to surface datum/sea 1 evel. Hydrocarbons tend to accumulate in "Highs". The term is also used on a regional basis, where rocks of one geological era are nearer the surface over a broad area. Hold up The quantity of hydrocarbons which is retained, in normal operations, in the process lines and vessels of a plant. Hole opener A large-diameter drilling bit. Hole Temperature Formation temperature at a given depth in a well. Hooks                    The part of the travelling block of a drilling rig from which the swivel and drill string or other load is suspended. Hook-up                     The activity following offshore development installation during which all connections and services are made operable f o r commissioning and "start up".       Horizon The formation at a given depth in a well, usually identified by geological age, e.g. "Middle Jurassic Horizon". Horizontal Drilling        A technique for deviating wells through up to 900 from the vertical. While the main purpose of normal deviated drilling is to "reach" remote parts of a reservoir, with horizontal drilling the purpose is to keep the well bore within a given productive horizon or formation, to increase potential productivity. Horst         A structure such as a fault-block, which has become up-thrust from its original surrounding geological setting. Hot pass A Filler bead-See Bead. Hottap inserting a branch line into a pipeline or vessel which is still in operation. Huff and Puff A steam-injection method of Enhanced Oil Recovery. Hundred year Storm For construction design purposes, the worst weather conditions that can be statistically predicted within a hundred-year period. Hybrid platforms are combination structures of concrete and steel with the base and storage area (where applicable) constructed in concrete, and the legs and deck constructed in steel. The structures remain on location under the gravity principle Ð i.e. relying upon its own weight to keep it in place on the sea bed. Hydrates    Compounds   of    water   with    another Substance e.g. natural gas in wells or a pipeline. They may cause plugging or corrosion. Hydrocarbons are a group of compounds including oil and gas which consist primarily of hydrogen and carbon. Any compound or mix of compounds, solid, liquid or gas, comprising carbon and hydrogen (e.g. coal, crude oil and natural gas). Hydrocracking     A catalytic cracking process using hydrogen and a catalyst. Hydrodesulphurisation (HDS)       Process to remove sulphur from molecules, using hydrogen under pressure and a catalyst. Hydrodynamic In the oil and gas industry these studies apply mainly to the migration of hydrocarbons in the earth's crust. Hydrophones The instruments which detect returning sound waves in offshore seismic survey sonar operations. Hydrostatic Pressure/head The pressure exerted by a column of liquid at a given depth, such as that exerted by drilling fluid in a well. Hydrostatic Testing Press used for re-testing vessels by pumping water into them. Hydrobaric Welding Chamber       Welding under high pressure conditions, i.e. subsea in an air chamber (Hyperbaric Chamber) similar in principle to a diving bell. Hyperbaric chamber is also the name given to a pressurised surface chamber or habitat in which returning deep divers are gradually reacclimatised to surface pressure. Hydrogen   The lightest of all gases, occurring chiefly in combination with oxygen in water. Hydrogen combines with carbon to form an enormous variety of gaseous, liquid and solid hydrocarbons  Hydroskimming refinery A refinery with a configuration including               only   distillation,  reforming  and   some hydrotreating. Hydrotreating                             Usually      refers      to       the hydrodesulphurisation process, but may also be applied to other treating processes using hydrogen. I Ice Platform An 'ice island' strong enough to support drilling operations, artificially created by spraying sea water to freeze on top of an existing ice surface. Idea Statement A framework which ensures the idea itself has been correctly stated and all significant parameters addressed IEA (International Energy Agency)  Established in 1974 to monitor the world energy situation, promote good relations between producer and consumer countries and develop strategies for energy supplies during times of emergency. Igneous rocks  Rocks formed from the solidification of molten magma. Impermeable Rock                                    A rock with restricted or Poorly communicating pore spaces, such that hydrocarbons will not flow through it. Impressed Current Protection The active, or 'Anodic' method of preventing corrosion in submarine steel structures. Unlike the cathodic protection system, the self- potential of the structure is counteracted by passing a large low voltage current through the surface to be protected. Inclinometer A down-hole instrument for measuring the angle from the vertical or 'slope' of a deviated well. Independent Ideas Ideas which are not required for other ideas and do not require any prerequisite ideas Independent Producer An expression describing an oil producer who sells his production on the market, not having his own refining facilities. It has come to be applied to all exploration and production companies apart from the large vertically integrated ones, and those national ly-owned or controlled. Inert Gas                       Chemically unreactive gases used to flood compartments where there is fire or imminent danger of fire. Inert gases are also used in the mixture breathed by divers. Infill Drilling Production wells drilled between existing wells to increase recovery of hydrocarbons. Inflation Factor                       Calculates the purchasing power of money; what additional monies are needed to purchase the same goods in the future, derived from the Inflation Rate, the percent change in some price index from one year to the next. Inflation Rate The percent change in some price index from one year to the next. Influence Diagram A tool to assist in identifying factors to consider when analysing the alternatives to a particular idea. Important in identifying key variables and  relationships in the decision problem Inhibited Mud Mud containing chemicals to prevent loss of water which could damage surrounding formations, and cause build up of filter-cake in the well. See Differential Pressure. Injection Well (Injector) Sometimes called an 'input' or 'service' well. A well through which water or gas is injected to maintain reservoir pressure and improve A sweep' or areal recovery of reserves. In Place Description of the total hydrocarbon content of a reservoir, as distinct from 'Reserves' which can be 'recovered' or produced. Oil or gas in place (01P, GIP) before the start of production is known as Oil or Gas Originally in Place or Initially in Place. (e.g. STOOIP = Stock Tank Oil Originally in Place; G11P = Gas Initially in Place). Inside Preventer A blowout preventer which is fitted to the inside of the drill-string. Instrument Pig A pipeline pig fitted with monitoring and gauging devices to check for damage or distortion of the line. Interface The term is widely applied in the oil and gas industry as in other industries. However, usage specific to oil products is in the interface between two batches of different products in a pipeline system. Unless separation is critical and maintained by an intervening pig or sphere, the products are allowed the small amount of commingling that occurs, and the combined product or 'interface' is drawn off separately at its destination. Internal Rate of Return (IRR) Discount rate at which the NPV of a project is zero. Also called Earning Power (EP) or RTEP. It is used mainly in US companies Interruptible gas Gas made available under agreements permitting the termination or interruption of delivery by the suppliers, usually for a limited number of days in a specific period. The opposite is "firm gas". Interstitial water        is the water present in the pores and/or fractures in the oil or gas- bearing zone of a reservoir rock. IPIECA International Petroleum Industry Environmental and Conservation Association. Isobath 1 .          A line connecting points on the sea bed of equal depth below the surface-a sea bed contour line. in mapping subsurface geology, a line connecting points on the top of a formation  of equal depth below surface datum/sea level. Isochore    In a reservoir a line joining points of equal vertical thickness. Isomers Compounds which have the same number and types of atoms in each molecule, but differ in molecular structure, e.g. Butane and iso-Butane, Octane and iso- Octane, etc Isopach A line joining points of equal stratum thickness. Reservoir formations are sometimes mapped in this way. J Jacket    1. The leg-structure of an offshore steel-piled platform.  2. A concrete coating applied to add weight  to submarine pipelines. (See Cement).  Jacket platforms are generally constructed of tubular steel, and are kept in position over the oil field by the use of steel piles driven into the sea bed. Jack Rabbit                      A gauge which is run through casing or tubing before use to check for correct sizing and freedom from obstruction or distortion. Jack-up Drilling rigs, production barges, etc. which once floated onto location can raise themselves clear of the water by 'jacking' themselves up their legs. They then offer the operating advantages of fixed platforms but unlike piled steel structures, their stability and load capacity depends on the strength and stability of the sea bed, and closely underlying strata. Jars                    1. Down hole tools inserted in the drill-string when fishing to jerk or jar the fish free by repeated sudden blows. They may also be used while drilling to avoid the drill-string becoming stuck. Artificially made cavern storage in a salt rock formation. Joint A single length of pipe. Coupled or welded to other lengths, joints become a string. The term joint may also refer to the couplings or joints themselves. Joint Operating Agreement (JOA)                           The document governing operations in a Joint Venture, of prime importance to all participants as under it they secure, or may lose, rights to production etc. A typical Joint Operating Agreement will include sections to cover most or all of the following topics: - Scope, Duration, Legal status - Interests rights and duties of the Operator and other participants - Management structure and voting procedure - Approval of Operating Programmes and Budgets - Cash contributions, costs and accounting - Control and custody of joint properties and equipment - Sole Risk, Default, Withdrawal, Assignment, etc. - Disposal of Petroleum -                        Confidentiality, Force Majeure, Litigation, etc. Joint Venture A common form of risk-sharing in Oil and Gas operations, especially exploration and production. Although they may have many of the characteristics of partnerships and are often referred to as such, they are usually legally constituted specifically to avoid partnership implications. See also Joint Operating Agreement. JARS Down hole tools inserted in the drill-string when fishing to jerk or jar the fish free by repeated sudden blows. They may also be used while drilling to avoid the drill-string becoming stuck. 2. Artificially made cavern storage in a salt rock formation  Joule Unit of measurement. The work done when a force  of 1 newton is applied to an object, displacing it through a distance of 1 metre in the direction of force. JP Fuels                              Fuels produced to specifications for jet propulsion (aircraft) use. Jug 1. A geophone. A 'jug hustler' is the member of a land seismic survey crew who places and retrieves geophones. Junk 1. Any small unwanted object 'lost' down a well. 2. To discard or scrap unwanted equipment. 'Junk condition' tubulars, for instance, are no longer fit for their intended use.  Junked       A well is cemented in and side-tracked, or abandoned, when attempts to retrieve equipment lost down hole fail. K Kelly The 'Square Section' pipe at the top of a drill string (sometimes Hexagonal). Another name is the Grief Stem. It fits into the 'squared' hole in the rotary table, which in turning it imparts torque to the drill string. Kelly Cock     An emergency 'blowout preventer' valve inserted between the swivel and the kelly. Kelly Spinner A mechanism attached to the swivel for rotating the kelly in or out of the top joint of drill pipe, e.g. when adding another stand. Kelly Valve (lower) An automatic valve at the lower end of the kelly which closes when the kelly is disconnected from the drill-stem, preventing spillage of mud. Kerogens Organic material from which oil or gas matures with time, under burial temperatures and pressures. They differ with origin-e.g. marine seaweeds, or terrestrial trees. Of the marine types, the presence of Algal Sapropel and Waxy Sapropel in a formation is prospective for oil, while of the terrestrial types, Vitrinite is generally prospective for gas, and Inertinite is not prospective. In addition the degree of reflectivity of Vitrinite samples is used as an indication of the maturity of a formation for the presence of hydrocarbons. Kerosine (kerosene)      A medium-light oil from the oil refining process intermediate between gas oil and gasoline; used for lighting and heating and as fuel for jet and turbo-prop aircraft engines. Kick Off To start the planned deviation of a well from the vertical. The depth at which this occurs is the Kick-Off Point (KOP). Kill/Killer Well 1. In normal operations, to kill a flowing well is to inject mud, etc, to the density needed to overcome reservoir pressure, thus stopping the flow for e.g. maintenance or modification work. Getting under control a well which has 'blown out'. A Killer Well is one drilled near a blowout, and deviated into or close to the blowout well, to inject mud, etc. to kill it. This is usually because the blowout has caught fire. Kilocalorie A thousand calories. A unit of heat used in the chemical processing industry. Kilowatt hour (kWh)    Unit of measurement in electric power. One kilowatt hour is equivalent to 0.0949 cubic metres of gas.  Kitchen  A colloquial term for rock deposited, in  conditions rich in organic sediments, which with the necessary burial history has become a significant source of hydrocarbons. These may have migrated to traps elsewhere. Knocking A metallic rattling sound in an engine caused by a mismatch between the fuel characteristics and the engine's design, particularly its compression ratio, resulting in pre-ignition (also known as 'pinking'). Knock-Out Drum   A drum or other process vessel used for rapid separation of water, etc. from a stream of hydrocarbons.  Knuckle Joint                          A universal joint in a drilling tool for deviated drilling which enables the bit to rotate at an angle to the existing borehole. L Landing Casing Lowering a string of casing into a well, to rest on the 'step' in the hole where drilling at a smaller diameter commences. Lay Barge/Pipelay/Pipelay Barge/Lifting                           A vessel designed for welding together pipelines and laying them on the seabed. A Reel Barge lays previously connected lengths of pipe from a reel. Lean gas or dry gas                                Gas with relatively few hydrocarbons other than methane. The calorific value is typically around 1,000 Btu per scf, unless there is a significant proportion of non-hydrocarbon gases present. Lease                       In the oil and gas industry, a legal instrument giving the right to explore/exploit acreage, primarily onshore. 'Lease operations' has come to mean any exploration production field operation. Lens A body of potential reservoir rock enclosed on all sides by sealing strata, so-called because frequently lens- shaped.  License   A right to explore for and/or produce  hydrocarbons issued by a Government agency, where rights to underlying minerals are not the property of the landowner. Exploration, drilling, development, etc. may be licensed separately, over varying lengths of time. Many licences require part-relinquishment of acreage after an initial period or "primaty term" and make the operations subject to the hydrocarbon policy of the country concerned. Various other forms of permit or authorisation affecting operations. Licence block A section of continental shelf area bounded by latitude and longitude lines, generally at one degree intervals, and subdivided into smaller areas. The 'licences' are sold to companies giving them oil exploration rights. Licence round A period during which a state offers and then allocates a number of specified areas within its national boundaries to oil companies. Lifo The last-in-first-out method of inventory valuation, chiefly significant in the oil and gas industry because historically the basis of US Tax computations. Lifting 1. Collection of a production shipment of crude oil etc. at the point of sale. Also covers bulk movements of any hydrocarbon against, e.g. contract entitlements. Stimulating production flow from a well. Light Crude Generally applied to crude oil with an API gravity of 30 degrees or over. See American Petroleum Institute. Light Ends                      The least dense, more volatile parts of a crude oil stream in distillation. Lightening See Lightering. Lightering                     A ship-to-ship cargo transfer operation to enable a vessel to enter a draft-restricted port. Light fractions  The low molecular weight, low boiling point fractions that emerge from the upper part of the fractionating column during oil refining. Line Fill The volume of oil or gas which is needed to fill a pipeline before any deliveries can be made, representing a permanent inventory requirement. Line pack The ability to increase the amount of gas in a pipeline by increasing the pressure above the normal pressure of the system, but still within a safe limit. Used as a method of peak or diurnal storage. Liquified Natural Gas (LNG) Natural gas that for ease of transport has been liquefied by cooling to approximately minus 161øC at atmospheric pressure. Natural gas is 600 times more bulky than LNG. It is predominantly composed of methane.  It is held in a refrigerated liquid state under pressure for transportation and storage. Natural Gas is processed into LNG by first removing carbon dioxide, water and heavy hydrocarbons which would freeze (hydrate) at cryogenic temperatures. The purified natural gas is then chilled to minus 161 degrees Celsius at which temperature it condenses into a liquid, 1/600th of its original gaseous volume. LNG is clear colourless and weighs about half as much as water. Lithology The study of rocks and hence the description of different formations encountered by a well. Live Oil   Crude oil containing volatile gases. Lloyds   Chiefly refers to the Certification authority. LNG carrier   A tanker specially designed to carry LNG,   fitted with insulated pressure tanks made of stainless steel  or aluminium. The load is refrigerated to -162°C.  LNG terminal  A receiving station for LNG shipments, typically with storage and regasification facilities. LNG train   An LNG plant comprises one or more LNG trains, each of which is an independent unit for gas liquefaction. It is more cost-effective to add a train to an existing LNG plant, than to build a new LNG facility (known as a greenfield project), because infrastructure, such as ship terminals, does not have to be built for a new LNG train   Local Drainage The movement of reservoir immediate vicinity of a flowing well. Location The site of a well, or other operation. Log/Logging etc      There are various applications, but chiefly: 1. Written chronological records such as shift logs, maintenance logs, tour sheets, and mud logs which also record cuttings recovered from a well. 2. Various devices for taking measurements of formations, physical conditions, and fluids encountered by a well, together with the records produced by them. The main types of well logs, are  Electrical, Magnetic, Mechanical, Sonic, Nuclear Lost Circulation Failure to recover to the surface all the drilling fluids at the same rate as they are pumped down a well, usually because of escapes into surrounding formations. Casing would normally be set through the relevant formation before proceeding. Liquified Petroleum Gas (LPG) is a light hydrocarbon which is gaseous at normal temperatures and pressures. LPG is composed mainly of propane and butane  or a mixture of the two which may be wholly or partially liquefied (as with LNG) under pressure in order to facilitate transport and storage. LPG can be used for cooking and heating or as an automotive fuel. Load factor         In gas contracts, the ratio of the Daily Contract Quantity and the maximum daily delivery capacity.  Load-on-top A system of cleaning tanks in an oil tanker by collecting washings in one 'slop' tank, allowing the water to separate from the oil, then discharging the clean water overboard, leaving the oil residues in the tank and minimising pollution at sea. Logic Tree A framework useful in disaggregating an idea into manageable chunks and in focussing work on core issues only. Logs   See wireline logs. Loss Carry-Forward                      A fiscal arrangement whereby losses incurred in certain years are offset against profits made in later years. LTI (Lost Time Injury) A measure of safety performance. Luboil Lubricating oil used to grease and ease the working of mechanical joints and moving parts. M Magma The molten material that makes up the Earth's crust. When extruded onto the Earth's surface and cooled it becomes igneous rock. Magnetic Particle Testing  A non-destructive testing method whereby the object is magnetised and minute particles applied externally. Cracks, etc. can be discerned at the surface. Welds in wellheads, etc. can safely be examined in situ. Magnetic survey A preliminary exploration technique based on the relatively low magnetic field of sedimentary rocks.  This measures variations in the earths magnetic field caused by the presence of rock structures and is used to detect sedimentary areas.  This type of survey is usually carried out by air. Majors The world's largest privately / publicly owned oil companies (Shell, Exxon, Texaco, Mobil, Chevron and BP). National oil companies can be much larger. Make Up / Break Out To assemble/screw together the sections of joints of a string of pipe. 'Breaking out' is the opposite. Manifold An assembly of pipework with several branches to gather fluids from, or distribute them to, different points. It usually incorporates valves so different flow patterns can be selected. Marginal A well, development, etc. whose commercial profitability is in doubt. Market Factor                           A factor in the cost escalator for a particular commodity, which recognises that it may escalate out of line with inflation due to market conditions. Marine riser A pipe that connects an offshore platform to a sub-sea wellhead or pipeline for drilling or production purposes. Master Bushing  The collar which fits into the rotary table and through which the kelly passes. Mat / Mattress                            A structure placed on poorly consolidated, soft or unstable seabed as a footing for jackup rigs, etc. Maturity The function of burial pressures, temperatures, and time which determines whether a source of hydrocarbons will provide oil or gas.       Maximum Exposure The maximum cash deficit or the maximum amount of money at risk. Mean Success Volume (MSV) the weighted average of the possible hydrocarbon volumes as represented in the Expectation Curve (ibid) above the cut-off volume. The latter can be taken as zero, in which case the MSV is the weighted average of all technically possible volumes. If an economic cut-off volume is used (below which development is uneconomic) this results in a higher MSV and a lower POS. It is essential therefore to stipulate the cut-off used when quoting the MSV. MD is the linear distance of a well measured along its drilled projection. Median Line The boundary between the offshore mineral extraction jurisdictions of two states, by convention drawn equidistant from the nearest points of land on each side. Mercaptans     Strong-smelling compounds of carbon, hydrogen and sulphur found in gas and oil. Sometimes added to natural gas for safety reasons. Metamorphic rocks  Rocks changed considerably under the action of pressure, heat, and water has become dense and crystalline, e.g. slate, gneiss, marble, etc. Meter A mechanical device for automatically measuring and recording quantities of gas. Methane (CH4) The smallest hydrocarbon molecule with one carbon atom and four hydrogen atoms. It is the chief constituent of natural gas, but also occurs in coal beds, and is produced by animals and the decay of vegetable material. It is a light colourless, odourless flammable gas under normal conditions. Methane is the first member in the alkane (paraffin) series. At atmospheric pressure, it liquefies at -162°C. Methanol (methyl alcohol)      An alcohol used as a raw material in a wide range of industrial and chemical processes. Migration 1. Hydrocarbons are often found in formations other than those in which their organic source was deposited. This movement often over considerable distances is known as migration. A process applied to data recorded, e.g. in a '2-J' seismic survey, to adjust for the effects of the "oblique" angle at which it was gathered. Mill   A bit for cutting through steel obstructions in a Well such as 'fish'. Milliard Synonymous with billion (109). Millidarcy See Darcy. Mill Scale   Oxides which form on the surface of a steel plate after heating during manufacture. Miscible Flooding An injection/displacement process developed recently to obtain greater oil recovery in many reservoirs. Miscibility is the ability of two or more substances to mix, without the existence of an interface. The fluids are injected together into a reservoir in a secondary or tertiary recovery programme e.g. Gas and LPG, or Carbon Dioxide followed by water. MJ/MMJ Megajoule; equivalent to one million watts. MMBBL Million barrels. MMBTU Million British thermal units. MMSCF Million standard cubic feet. MMSCF/D Million standard square feet per day. MOD (Money of the Day): This is the money we get paid in and spend. The same amount of MOD buys less and  less each year because of inflation. It is also the type of money used in tax calculations and in most financial plans or budgets. MOD inflator The number by which we divide the MOD cashflow of a given year to convert it to Real Terms. It is the ratio of the price of a “basket” of goods in that year to the price in the Reference Year. Modules A separate section or box-like compartment of the 'top side' of an offshore construction, as far as possible self-contained, designed to be lifted into place and connected to other modules offshore. Modern large capacity cranes have meant that modules can be fewer, larger, more efficient, and less costly to the project. are packages of equipment for installation on an offshore production platform. Molecular Sieve                      A process of separating hydrocarbon fractions etc. by passing the feedstock through successive absorbent substances which offer differing degrees of resistance to its passage. Molecule The smallest particle to which a compound can be reduced without losing its chemical identity. Monomer                    A single molecule which can be chemically joined into long chains known as polymers. Multinational company (MNC) A company with investments and operating activities in many countries around the world. Monopod A small offshore platform, resting on a single columnar 'leg', mainly for small satellite developments in shallow waters. Moonpool A 'well' in an offshore vessel, open beneath the surface of the sea at the lower end, through which depending on the vessel's function, the drill-string, risers, or divers etc. can be lowered in calm surface conditions independent of sea state. Motion Compensator                     A heave compensator. Fitted to cranes etc. to counteract vertical motion caused by the sea. Motor Octane Number See Octane Rating Mousehole The tubular 'hole' in the floor of a drilling rig in which the next stand of drill pipe is stored ready for addition to the drill string. MSCF Thousand standard cubic feet. MTBE ( Methyl Tertiary Butyl Ether) A hydrocarbon product significant as one of the major leadfree Octane enhancers for gasolines. See Anti Knock Compounds. Mud Is the name given to drilling fluid which is mainly a mixture of water, or oil distillate, and 'heavy' minerals such as Bentonite or Barites. Mud is pumped into a well at densities calculated to provide a hydrostatic pressure sufficient to overcome downhole formation pressures. (See e.g. Gas Kick). In addition, the mud is continuously circulated down to the bit, and returns in the annular space outside the drill-string, bringing with it rock cuttings for inspection and keeping the well clean. It is also engineered to maintain a thin protective layer of filter- cake on the bore hole wall, without excessive weight which would decrease the weight on the bit and hence penetration (see Drill String), and also possibly lead to differential sticking and formation damage. Mud is pumped from the mud pit (or tank) via the standpipe, rotary hose and gooseneck to the swivel, and into the drill stem. On return from down hole it is recovered and rock cuttings removed by the shale shakers before re- circulation. To Mud Up is to increase mud weight and downhole pressure. To Mud Off is to seal off a formation with heavy filter cake. A Mud Log is the record of mud       make-up and analysis of cuttings recovered. The composition of mud used in a well is normally supervised by a Mud Engineer. Mudline The sea bed, or bed of any body of water where drilling is taking place. Mud logging   This is the recording of information derived from examination and analysis of formation cuttings made by  the bit and mud circulated out of the hole.  A portion of the mud is diverted through a gas-detecting device and examined under ultraviolet light to detect the presence of oil or gas. Mullett An inexperienced investor in oil exploration. Multiphase Flow Simultaneous flow of liquid and gas, or of different liquids, through a pipeline or other vessel (e.g. oil/gas, gas/water, oil/water). Multiple Completion    A well perforated and completed to produce simultaneously but independently from more than one formation. Also known as a Multipay Well. N NAFTA   (North American Free Trade Agreement): its members currently comprise Canada, Mexico and the United States. Naphtha      is a volatile, flammable liquid hydrocarbon distilled from petroleum and used as a solvent or fuel. Native gas is gas originally discovered in a reservoir as distinct from injected gas. See also Associated Gas. Natural Depletion is producing a reservoir by means of its natural press u re-without pressure maintenance. (Also Flush Phase, Primary Production, etc.) Natural gas     is a gaseous mixture of light hydrocarbons comprising predominantly of methane.  It is often found with crude oil, when it is known as associated gas. a) A mixture of generally gaseous hydrocarbons occurring naturally in underground structures. Natural gas consists mainly of methane (80%) and significant proportions of ethane, propane and butane. There will always be some condensate and/or oil associated with the gas. b) The term is also used to mean treated gas which is supplied to industrial, commercial and domestic users and meeting a specified quality. Natural gas liquids (NGL)   Light hydrocarbon fractions distilled from wet gas streams, usually spiked into crude lines for transportation purposes. Natural Period is the time that elapses between successive occurrences of any phenomenon, such as two successive wave-crests or the resulting movements of heave, roll, etc. of a floating vessel. Neoprene   A mixture of natural and petroleum-based synthetic rubber highly resistant to chemical attack. Netback   The value of gas sold to the customer at the burner-tip, less the cost of transportation through the pipeline system and cost of production. Net Present Value (NPV) A financial technique which estimates the value creation of a project by estimating expected cash flows and then discounting these future free cash flows at the appropriate risk - adjusted opportunity cost of capital. NPVs of different projects are additive.  Net Profits Interest   A low-risk form of participation in which the beneficiary, who is usually 'farming out' his interest, makes no further contribution to the cost of operations but is entitled to a share of any net profit on production revenues after deduction of all costs, including in some cases, interest. Net Revenue Interest                            Another form of net profits interest but normally without deduction of capital costs or financial charges. Neutron Log   See Log. Nipple etc.   A short length of pipe with connections at both ends. To Nipple Up is to assemble pipe valves etc. especially a blowout preventer. A Nipple Chaser is a materials man whose job it is to obtain and have ready for shipment to the rig the various tools, supplies, etc. needed. Nodding Donkey   The colloquial name for conventional onshore wellhead production beam pumps. Node The specially strengthened junction of tubular components in a conventional steel platform jacket. There are several on each leg and also at the meeting of cross- members. Non-associated Sometimes called unassociated gas. Dry gas that is not associated with oil in a productive reservoir, or where only gas can be produced economically. Non Destructive Testing (NDT)   Methods of inspecting and testing the quality or integrity of vessels or equipment which do not involve removal or testing to destruction of representative sections. Non-Operator   Any equity participant in a Joint Venture operation other than the Operator. Non Recourse Financing   Lending to a participant in a development project on the security provided by the development revenues and assets alone. Sometimes the financing covers participations in several development projects, which provide mutual security but without further recourse to the borrower. Nuclear Interface Log   A 'gamma-ray' log. See Log. NOx Nitrogen oxides. O OPEC                      Organization of Arab Petroleum Exporting Countries. Obligation Well   A well undertaken as part of the process of earning a concession. Obo Vessel   An Oil/Bulk Ore carrier, a versatile form of tanker. Observation well   This is a special well drilled to allow observation of fluid levels, changes in pressure etc., within the reservoir as production proceeds. Octane number                      A measure of the resistance to pre- ignition (which leads to knocking) of a gasoline. Odorant                      Substance such as mercaptan with a characteristic smell, added to odourless natural gas or NGLs when they are used as s fuel, in order to enable detection.       OECD   Organisation for Economic Cooperation and Development, based in Paris. Ofgas Office of Gas Supply, the UK gas industry regulator. Off-peak The period during a day, week, month or year when the load being delivered by a gas system is not at its maximum volume. Offset Well   A well drilled to 'mirror' a production well drilled near the boundary of a neighbouring concession, on a common reservoir, in order to secure a due share of production. Offsite Facilities (Offsite)   Ancillary or service plant which is distant from the main process plant. (e.g. Water treatment, power generation, laboratory etc.) It is sometimes applied to service installations in general, particularly at refineries. Offshore Installation Manager (O.I.M.)   The person on an offshore platform with statutory responsibilities for safety, etc., similar to those of a ship's captain. Offtake The point in a gas distribution system where gas is taken by supply pipe to a major consumer. Oil-Based Mud   Drilling mud in which the solids are suspended in a hydrocarbon distillate rather than water. This has operational advantages particularly in deeper or technically difficult wells, but can make the detection of formation hydrocarbons more difficult. Oil Column/Gas Column The vertical distance between points of highest and lowest known oil or gas. in a reservoir. Oiler An oil well, particularly an oil discovery well. Oil Field   1.  A group of hydrocarbon reservoirs in a common geological setting. A single reservoir, the subject of actual or planned development. Oil gasification The conversion of petroleum into gas to be used as a fuel Oil Geology   Specialised geology which deals exclusively with sedimentary basins and the sources of hydrocarbons. Oil in place (OIP) The estimation of the real amount of oil in a reservoir, and so a higher figure than the recoverable reserves of the reservoir (see recoverable reserves and recovery factor). Oil Patch  A colloquial reference to exploration and production activity. Oil Province   See Petroleum Province. Oil shale A compact sedimentary rock impregnated with organic materials (mainly kerogen) which yields oil when heated.   Oil Spill   Any accidental emission of liquid hydrocarbons, from general shipping, oil tankers, or operations onshore or offshore. Oil String   The inner or production string of casing in a well. Oil/water contact (OWC)        The lower end of the oil column in a reservoir with underlying water.  This may be graduated or occur in formations where it is hard to detect. Olefins A class of hydrocarbons, including ethylene and propylene, of particular importance as feedstock to the chemical industry. See also: polypropylene.  On-Line 1.   Any vessel or equipment which is a normal and permanent part of the operation (e.g. an online computer). 'On Line' can also mean in working order, serviceable. On Stream   When production is flowing, or plant is in operation.  On The Brake   In control on the rig floor, e.g. the driller. On the brake refers to the control of weight-on-the-bit etc. (See Drill String) OPEC                   Organisation of Petroleum Exporting Countries. Formed in 1960, its member countries are Algeria, Ecuador, Gabon, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates and Venezuela Open Flow Producing a well without chokes or beans. Unrestricted              production  normally  for   testing  or maintenance purposes. Open Hole   An uncased section of well borehole. Operating Interest An equity interest in concession, which pays an appropriate share of the costs and receives an equivalent share of residual income after prior charges such as royalties. Operator A company, organisation or person with the legal authority to drill wells and extract hydrocarbons. A drilling contractor may be employed to undertake the drilling itself. The operator is often part of a consortium, and acts on its behalf. OPOL (Offshore Pollution Liability Agreement) An industry co-operative insurance and self-insurance scheme between operators in the European continental shelf and adjacent coastal areas covering costs of major pollution clean up. Opportunity Focal Point (OFP)                             Responsible for deliverables. Option Value                     A way of valuing a project's addition to flexibility in decision making that is not caught by strict NPV analysis. Types of flexibility to be valued include the option to defer an investment, to expand (or contract) the scale of a project, to abandon a project, or to start up and shutdown an ongoing operation. Asset options are especially valuable in valuing businesses that develop and extract natural resources. Organic/Organic Chemicals   Substances derived from living organisms, such as oil in the natural state. Orifice Meter   An instrument which measures the flow of a fluid in a pipeline by monitoring a controlled flow through a small aperture. 0-Ring   A ring shaped gasket for flanged pipe joints. Orogeny  The process of shrinking, cooling and 'wrinkling' of the earth's crust, leading to the formation of mountains, synclines, anticlines etc. Outcrop   The appearance of occurrence of a rock formation at the surface Overheads   1. The 'light ends' produced from the top of a distillation vessel.  2.  Standing expenses not related to, or variable with, specific operations. Overlift   Collecting more crude oil etc. than a production participant or purchaser is entitled to at any one time. See also Underlift Overriding Royalty   A royalty payment from production revenues before any deduction for costs, taxes, etc. Overshot   A fishing tool with a socket to fit over, enclose, and grip the top end of the fish for pulling out.  P  Packer  A seal used to isolate a section of a well, e.g. for testing or production from one of several formations. Packers are also used in operations such as cementing and acidizing. Palaeontology   The study of fossil organisms related to their geological setting. Palynology   The study of pollens and plant spores. Identification of fossilised forms of these in a geological formation can help determine the environmental origin of sedimentary rock, and periods of exposure as land rather than sea bed. Paraffin UK name for a premium kerosine; used in lamps and space heaters. Participation  This usually refers to rights retained by a state when granting a concession, primarily to acquire part of the production at stated terms, but sometimes also to participate on a full equity basis in any production development. Pay-As-You-Go Date The date the project starts to pay its own way. Pay Out   When accumulated revenue from an operation equals the accumulated cost to date including investment cost.  This is normally expressed as a period of years from starting to earn revenue. Pay Out Time The time that the original investment has just been recovered. Pay Sand is the producing formation, often one that is not actually sandstone.  It is also called pay, pay zone, and producing zone. Pay String The production or inner string of casing. Pay Zone/Horizon A formation containing producible hydrocarbons. Peak load The maximum load produced or consumed by a unit in a stated period of time. Peak lopping See peak shaving. Peak shaving Increasing the normal supply of gas from another source during emergency or peak periods. Perforate      is to pierce the casing wall and cement to provide holes through which formation fluids may enter or to provide holes in the casing so that materials may be introduced into the annulus between the casing and the wall of the borehole.  Perforating is accomplished by lowering into the well a  Perforating Gun (cylindrical tool) loaded with explosive charges which are triggered opposite the pay zone, perforating the casing in many places. Permeability     is the degree to which a rock will allow liquid or gas to pass through it.  It is a function of the shape of the capillary pore spaces and the degree to which pores are connected. Petrochemical     A chemical derived from petroleum or natural gas (e.g. benzene, ethylene). Petrol See Gasoline. Petroleum The general name for hydrocarbons, including crude oil, natural gas and NGLs. The name is derived from the Latin oil, oleum, which occurs naturally in rocks,  Petroleum Engineer A specialist in the properties and behaviour of hydrocarbons in their natural reservoirs and under production conditions.  While a geologist normally provides estimates of hydrocarbons-in-place, a petroleum engineer would normally provide the estimate as to how much of it could be produced (recoverable reserves) under what conditions, and at what rate. Petroleum Province A large area where reservoirs show common origins and characteristics. Petrology The study of rocks, their origin, chemical an physical properties and distribution. PH  A scale of alkalinity or acidity running from 0 to 14, with 7 representing neutrality, 0 maximum acidity and 14 maximum alkalinity. Pig etc  Bullet-shaped, cylindrical or spherical capsules which are inserted into a pipeline flow and travel along it with the fluid.  Their primary purpose is to scrape the pipeline clean of rust, wax or other deposits, or in a gas pipeline, slugs of liquid from low points in the line. Caliper Pigs also measure the pipeline as they travel, and ‘smart’ or ‘intelligent’ pips contain various instruments to monitor pipeline condition and integrity.                     Pig Launchers                     and Pig Traps     are the arrangements of valves etc through which pigs are inserted into and extracted from a line. Piling refers to the steel ÒpinsÓ which are driven through specially designed slots on a jacket platform, and into the sea bed, often down to a depth of 150 feet (45 metres) or more. Pillow Tanks Collapsible synthetic rubber/fabric storage tanks which can be easily transported and deployed in eg military operations or difficult terrain. Pin                        1.  See Piling  2. The ‘male’ end in a threaded connection. Pinch-Out The thinning out and disappearance over a distance of a formation eg an oil bearing sandstone between layers of impermeable rock. Pinch-out trap   See stratigraphic traps.  Pinger                          A source of sounce (eg an ‘air gun’) for an  underwater seismic survey. Pinking See Knocking. Pipe Clamp In drilling, a collar fitted to a string of pipe to stop it dropping if the slips fail to hold it. Pipe Facing Machine                          A machine for cleaning and preparing the butt ends of pipe joints for welding. Pipeline A tube for the transportation of crude oil or natural gas between two points, either offshore or onshore. Pipeline capacity                      The amount of oil or gas required to keep a pipeline full, or the amount that can be passed through a pipeline over a given period of time. Pipe Rack   Where stands of drill pipe are stacked vertically in a derrick ready for use.  Racks or frames are also sometimes used to store tubulars horizontally in yards and on offshore decks, and when transporting them offshore. Pipe Ramp  A sloping ramp from the pipe storage area up to the working floor of a drilling rig. Pipe Rams   Hydraulic rams in a blowout preventer which are shaped to fit around the drill-stem and seal the annulus.                 Blind Rams           are designed in extreme emergency to shear through the drill pipe and seal the well completely.  PLAT An official concession map in the USA – hence any official concession map. Platform A fixed for floating offshore structure from which wells are drilled. Drilling platforms can become production platforms once the wells are producing oil. Platform equipment refers to all the equipment on a production platform.  The equipment includes such items as: module shells; accommodation areas; helicopter decks; water and gas separators; scrubbers; pumps; compressors; boilers; heating; ventilating and burning equipment; sewage   treatment  plants;   electrical; communication; navigational; fire-fighting and safety systems; well-head and hydraulic shut-down systems; cranes and flare stack. Platforming  A catalytic reforming process using a platinum catalyst. Plenum  An enclosure such as a control room where for safety reasons, the air pressure is kept higher than outside, to prevent infiltration by inflammable or poisonous gases. Plugging and abandoning a well (P&A)             On the completion of a well which is not to be immediately re- entered the operator will P&A, which is seal the well or part of with cement. Pogo Plan          A financing arrangement for high cost exploration. The investors usually take stock etc in a company set up for the purpose. Polycyclic Hydrocarbons   Hydrocarbons whose carbon atoms from a ring or rings eg Cyclohexane. Polyethylene A polymer formed by the joining of ethylene molecules; one of the most important plastics. Polymer      Two or more molecules of the same kind, combined to form a compound with different physical properties eg Polyethylene. Polypropylene A polymer formed by joining propylene molecules. See also: olefins.   Pontoon 1.  A flat-bottomed vessel (“barge”) for   transporting structures etc to an offshore installation site A submerged or semi-submerged part of a floating drilling rig structure designed to assist flotation, containing ballast tanks. Pool  1.  An Oil Pool is a reservoir or group of reservoirs sharing a common pressure system  2. In a refinery or blending plant, the Gasoline Pool is the average Octane value of the gasolines produced/available. Pop Up Buoy/Recall Buoy A buoy which is normally submerged but will surface in response to an acoustic signal.  Often used to mark the position of wellheads. (Also, colloquially, “Yoo hoo” buoy) Porosity           is the proportion of a rocks total volume occupied by voids between the mineral grains. Possible reserves An estimate of possible oil and/or gas reserves based on geological and engineering data from undrilled or untested areas. Posted Price       Official price of a type of crude oil for export from some producing countries.  Historically, they were the basis of tax assessment rather than the price actually paid. Post Implementation Review (PIR)            To compare implementation results against budget/plan, and to draw out and document lessons learnt.  Potentially Commercially Recoverable Reserves Reserves which can be commercially developed under not too high oil price scenarios. For this purpose it may be considered that Unit Technical Costs associated with developing the discovery should not exceed the current reference PSV. Pour point The temperature below which an oil tends to solidify and will no longer flow freely. Pour Point Depressant (PPD) Chemical compounds added to very viscous or waxy oil to prevent it thickening at low temperatures to the point where it will not flow. PPM Parts per million. Prairie-Dog Plant A small, basic distillation plant for use in remote production areas to extract locally needed fuels from the crude oil. Present Value (PV) The PV of an amount to be received at a specified future date is the amount of money we would need now which, after adding interest annually until the future date, would grow to equal the amount to be received. Pressure                     The force exerted by one body on another, either by weight (gravity) or by the use of power. Measured as force over area, such as newtons per cubic metre. Pressure Bomb A down hole pressure recording capsule used in well monitoring. Pressure Habitat A sealed chamber in which divers can rest between shifts without decompression. Pressure Maintenance The process of keeping reservoir pressure at the optimum level during production, normally by water or gas injection to replace fluids extracted. Pressure Vessel A tank or process chamber built to hold fluids under pressure whether for production, refining or other purposes. Primary migration   Nearly all sedimentary rocks contact a small percentage of organic materials from which the petroleum could be formed.  As pressure from overlying layers compacts these source rocks, the oil or gas droplets are squeezed out and joined together to form globules large enough to flow under pressure. Primary recovery occurs when the oil is produced as a result of natural reservoir pressure. See also: secondary and tertiary recovery. Primary Refinery Process The distillation of crude oil into its major components for further processing or sale ie LPGs and gases, naphtha, middle distillates, residual fuel oils. Primary Team                              The initial period of an oil or gas concession, during which, if the operator’s obligations are fulfilled, rights to a second term, often over a reduced area, can be acquired.  See also Relinquishment. Probable reserves                        An estimate of oil and/or gas reserves based on penetrated structures, but needing more advanced confirmation to be classified as proven reserves. Producer Price Index                                The price index number applicable to wholesale prices Production 1.  The full scale extraction of hydrocarbon reserves               (also   the    reserves   extracted)      2. Refinery/petrochemical operations resulting in a yield of products. Production Casing String   The innermost steel lining of a well cemented in place and perforated for production in       the pay zone. Note that production tubing is inserted inside this casing. Production Payment Loan   A loan repayable out of production from a well o r field. Production Plateau   The period during which a field is capable of producing at or near its maximum average rate. Production Platform/Facility   Production platforms are of varying types depending on environment (water depth etc. and reservoir needs). Semi-submersible and ship- shaped vessels developed from the respective off-shore drilling rig concepts are also used as production facilities. where several inter-dependent platforms are clustered in a development they are known as a Production Complex. Production Testing   A production test concerns the capability to produce (productivity) of a well and its effects on the reservoir produced. A production test may continue for several months where extensive data is necessary prior to final commitment to development expenditures etc. Production Tubing String   The string of pipe installed inside the cased production well, to a point just above the reservoir through which the fluids are produced. It may be 2" to T' diameter or more, depending on the production flow and pressures anticipated. Production Well/Producer   A development well specifically for the extraction of reservoir fluids. Production Wellhead and Tree   The assembly of casing head, tubing head, connections and well-control valves fitted to a producing well. The "Christmas Tree" is the name given to the complete assembly of valves, connecting flanges etc. Productive Horizon   A pay zone. See also Horizon. Productivity Index The continuous productive capacity of a well. The Index is measured as volume produced (e.g. barrels per day) divided by the drop in pressure (p.s.i.) to achieve that flow rate starting with a "shut in" pressure. Profiling  Shallow seismic surveying by echo-sounder techniques. Project finance     A method of financing in which the lender has a claim to receive loan repayments only out of the revenues earned by the project he helped finance. In this type of finance, the lender has no recourse to the borrower's other assets. Project Screening Value (PSV) the reference value of a standard crude (eg Dubai) as advised from time to time, and used for the economics screening in project evaluations. Propane (C3H8 or C3) A hydrocarbon, small quantities of which are found in natural gas, consisting of three carbon atoms and eight hydrogen atoms; a gas under normal conditions. Used as automotive fuel and for cooking and heating purposes. At atmospheric pressure, propane liquefies at -42°C. See also: LPG. Proppants      Sand, gravel or other particles or “beads” used in hydraulic fracturing of a formation, to allow oil to flow more freely by wedging into the cracks etc created and preventing them re-closing. Proprietary Data       Primarily data obtained from the owner of a seismic survey record under confidentiality undertaking.  It can also include all confidential information acquired as part of sole or joint operations.  Prorationing                           Restriction of production in a multi- concession system in proportion to field capacities and ownership interests.   This may be by government regulation or due to a period of under-capacity or eg maintenance in a pipeline system. Propylene (propene)  An olefin consisting of a short chain of three carbon atoms and six hydrogen atoms; a very important base chemical for the chemical and plastics industries. Proven reserves                      The quantity of oil and gas estimated to be recoverable from known fields under existing economic and operating conditions. PTD   Prognosed or predicted total depth of a well. Pull-in   Winching the end of a subsea pipeline or flowline into a connecting chamber or wellhead, or through a “J” tube riser guide to the platform deck. Pulling Casing Retrieving casing from a well (where possible) before abandonment. Pulling Out Retrieving and stacking the drill-string on reaching target depth. Pup Joint A joint of a pipe of non-standard length, to make up a string of tubulars to an exact required total length. Purging                     Cleaning the interior of pipes and vessels to eliminate inflammable matter, usually with a “safe” gas such as nitrogen. PVT Pressure/Volume/Temperature data usually related to a test of a reservoir formation or well. Pyramid Statement A communications tool to ensure a well supported and structured case is presented which follows a Recommendations - Synthesis - Analysis - Data sequence Q Quadrillion                             In the oil and gas industry, the U.S. definition is used, e.g. 1015            not 1024 as internationally accepted. Quiet Rig                           A drilling rig insulated and equipped to operate with minimum disturbance of sensitive onshore environments such as built-up areas.   QuitClaim   A document giving up an interest in a   concession or lease. Q Unit                       A unit used in overall assessment of energy resources. It is equal to 1T1 British Thermal Units (BTU). R Rabbit   A small pig for flowlines. Racking Board   See Tubing Board. Radioactive Log   See Log Ram   See Pipe Rams Rathole  A hole in the drilling floor in which the kelly joint is kept when not in use.  Raw natural gas Natural gas containing impurities and unwanted substances such as; water, nitrogen, carbon dioxide, hydrogen sulphide gas and helium. Before the gas is marketed, these are removed. Real Terms (RT) Money RT money is simply a tool that we use in economics. It is imaginary money that retains its buying power over time. In today's RT money, $5 would buy a decent hamburger, it will also buy a decent hamburger in 10 years time providing that the demand has not been distorted by a shortage of beef cattle or a change in eating habits. Real Terms Earning Power (RTEP) The discount rate of a project at which its NPV is zero. If the RTEP exceeds a project's cost of capital the NPV is positive; if the RTEP is less than the discount rate the NPV is negative. Reamer   A bit designed to enlarge a borehole.  It may be included in the drill string just above a conventional bit. Recall Buoy   See Pop-Up Buoy Recycling (Gas)       Re-injection of produced gas into a gas/condensate reservoir to maintain pressure for optimum recovery of condensates. Recovery factor is the ratio of the recoverable oil and/or gas reserves to the oil and/or gas in place in a reservoir. Recoverable reserves      Of the total oil in place only a proportion can be ultimately recovered, the amount being dependent on the permeability of the rock, the properties of the oil and the type of natural drive available.  At the extremes between 10% and 80% of the original oil in place can be recovered in primary phase, but the norm is 20-30%.  Thereafter, depending on the success of secondary recovery techniques the figure can be further improved upon, but the final figure for recoverable reserves will only be known once the field is in production. While this often results in an upgrading of the estimated recoverable reserves, there are many instances when the reverse has been true. Reef   A reservoir, usually limestone, deposited in marine conditions.  As the name implies, it is frequently elongated, and early high production may not be sustained without pressure support. Reef effect The increase in marine life on and around an offshore structure. Reel Barge     A vessel for laying underwater pipelines form a rotating drum large enough to hold a continuous length of pre-welded pipeline. Re Entry   Inserting the drilling, testing or logging string etc into the wellhead.  Reference Year As far as inflation is concerned this is the year on which the Real Terms money is based. RT money maintains the purchasing power that money has at the middle of the Reference Year. It is common to choose the year in which the Reference Date for PV calculations falls. If this is done, the “base” dates for inflation and for Present Value coincide. Refinery    A complex of facilities where crude oil is separated into light or heavy fractions, which are then converted into useable products or feedstocks. Reforming    A process which improves the anti-knock quality of gasoline fractions by modifying the molecular structure. When achieved by heat and pressure the process is known as thermal reforming, and as catalytic reforming when aided by a catalyst. See also: Knocking. Reid Vapour Pressure (RVP) A standard oil industry measure of vapour pressure in psi at 100°F (38°C).                                                                                                             Relief Well  A second well deviated from a safe distance  to a bottom-hole location close to a “blowout” well and produced so as to reduce the pressure in the blowout. See also Killer Well. Relinquishment   It is a common feature of government concessions or licences that at the end of the primary term a proportion, commonly half, of the area concerned must be released by the licensee (relinquished).  This encourages early exploration activity to identify the most highly prospective parts of the concession. Renewable                        energy     Energy  resources  that   are continually available or can be replenished (e.g. solar, wind, wave, biomass, hydroelectric, geothermal). Reserves                       See; proven reserves, probable reserves, possible reserves and recoverable reserves. Reserves-to-production ratio For any given well, field or country. The length of time that reserves would last if production continued at its current rate, at the current level Reservoir   A porous, fractured or cavitied rock formation with a geological seal forming a trap for producible hydrocarbons.  A common exploration maxim is that a prospective target must possess a related source rock, structure and seal. Reservoir Engineer   A Petroleum Engineer specialising in the behaviour or potential behaviour of reservoirs and their fluids under production conditions. Reservoir Pressure   The pressure at reservoir depth in a shut-in well. Residual Oil   The dense, viscous "Heavy Ends" of the barrel, remaining after extraction of higher-value fractions. Retrograde Condensation   In some reservoirs mainly deep gas/condensate reservoirs, (gas/oil ratio between 5,000 and 100,000 cu. ft. per barrel) where temperatures and pressures are high, a progressive decrease in reservoir pressure as result of production will gradually lead to separation of liquids (heavier molecules) from natural gases in the reservoirs. These liquids are mainly lost to production, being by passed" by the more mobile gas. "Recycling", reinjection of produced gas to maintain pressure, is used to postpone this problem until an acceptable proportion of recoverable liquids has been produced. Reworking a Well   Maintenance work on a well to stimulate production. This may involve cleaning out silt deposits etc., or stimulation techniques such as fracturing or acidizing. Rig  A collective term to describe the permanent equipment needed for drilling a well. It has come to include the onshore and offshore vehicles, mobile platforms, or vessels on which the equipment is installed. Rig Manager   Also Rig Superintendent, Rig Boss. The senior individual onsite in a drilling operation. He may also be an Offshore Installation Manager. Ring Fence   A fiscal segregation of revenues and profits from oil and gas production to prevent costs and losses from other corporate activities being offset against them, and production tax revenues "lost" thereby. Riser  A pipe through which fluids flow upwards, as from a subsea wellhead or gathering pipeline to the deck of a platform. Risers may be rigid or flexible (the latter more common for floating production facilities). Roller Bit   A rotary drilling bit which penetrates by pulverising the rock with its toothed wheels. Rotary Bit   See Bit. Rotary Hose   The mud supply hose from the standpipe to the swivel. Rotary Table   The heavy turntable at the centre of a drilling rig floor, which is rotated by the main rig power supply, and in turn rotates the kelly. Roughneck   See Drilling Crew. Round Trip   Recovering the drill string from the bottom of the well to the surface and returning it to continue drilling. This may be e.g. to replace the bit "Tripping" is arduous and interrupts "making hole". Roustabout   See Drilling Crew. Royalty/Royalty Oil   Royalties are payable on operations which are subject to prior rights of other parties, such as land owners of production leases, patent proprietors of refinery processes, etc.  Royalty Oil is taken by those to whom royalties are due 1n kind" in place of cash payment. Running-In/Running Casing   Inserting any tubular or tool into a well is known as "running-in". Assembling and lowering in a string of casing is "running casing". S Sack   Cement, mud chemicals and other solids used in drilling are supplied to the rig and measured into the well in Sacks (SAX). Sacrificial Anode      In a cathodic protection system, a block or bar of non-ferrous metal attached to the submerged part of a steel structure is gradually eroded in prevention of structural corrosion. Safety Boat  A small vessel, employed to remain in the vicinity of an offshore installation for emergencies such as “man overboard”. Sales gas      Raw gas, after processing to remove LPG, condensate and carbon dioxide. Sales gas consists of methane and ethane. Salt Dome   See Salt traps Salt traps    results from the intrusion of salt rocks into overlying sediments.  This intrusion often takes the form of cylindrical, steeply conical or mushroom-shaped masses of rock.  Porous formations if present are truncated and effectively sealed by the salt plug.  The salt plug, where it fails to penetrate upwards, can still have the effect of causing sedimentary folding, which could result in anticlinal traps. Sandstone is a detrital, sedimentary rock composed of individual grains of sand (commonly quartz) that are cemented together by silica, calcium carbonate, iron oxide, and so forth.  Sandstone is a common rock in which petroleum and water accumulate. Sapropel  See Kerogen Satellite Development/Platform/Well   An installation dependent on the existence and services of a gathering platform/facility.  They are usually relatively small but profitable because of the lower capital investment required per barrel of reserves. Satellite Navigation/Communications Communications satellites are now extensively used to “fix” or locate positions offshore to the accuracy necessary for oil and gas operations. Saturated Hydrocarbons                          Hydrocarbon molecules which cannot absorb any more hydrogen atoms without subdividing to release carbon valencies for further hydrogen. Saturated Oil  See Saturated Hydrocarbons, Fat Oil etc. Saturation Diving                     Diving performed over long periods at high submerged pressures.  Instead of depressurising after each shift, the diver lives in a pressure chamber either below the surface or hoisted onto the diving support vessel.  See also Decompression Chamber. SBM (Single Buoy Mooring) Also known as single point mooring (SPM), this consists of a single floating chamber moored near an offshore production platform to serve as a connection to a tanker. It has no storage capacity. See also: FSU (Floating Storage Unit). SCF standard cubic feet. Scouring  The process by which tides and currents carry away loose sedimentation etc from around a fixed object on the seabed such as a platform leg or pipeline. Scout  A person employed to glean information on results of seismic surveys and wells in an area. Scraper  A device for cleaning the inside of casing in a well, or as with a Scraper Pig, the inside of a pipeline. Scratchers                          Collars with wire “bristles” fitted to the outside of casing to remove filter-cake from the well bore and help ensure a good cement bond. Screen   A tubular “sieve” inserted into a well bore to hold back loose sand and rock, while letting oil and gas enter the well. Scrubber A separator for removing liquids and solids from a gas stream. Scrubbing                    The process of purifying a gas or liquid by washing it in a contact vessel. Seal   See Reservoir.  An impermeable fault or stratum of rock beneath or behind which hydrocarbons can accumulate. Secondary migration Long globules of oil are forced through pore spaces in the rock by the force of moving water.  It is usually forced upwards being lighter than water until it emerges at the surface or is trapped under a cap rock to form an accumulation of oil or gas. Secondary Porosity                            Porosity developed after the original deposition of a formation, for instance by the action of water on soluble components of the rock, or well stimulation techniques.  The flow of fluids through a reservoir               under  production conditions can   cause development of secondary porosity. Secondary recovery is used to supplement or replace primary recovery.  Various techniques are used, the most important being the injection of water or re-injection of gas to maintain reservoir pressure.  In modern practice secondary recovery is used earlier in the life of the field than was the practice in the past as this gives more control over production and better overall recovery from the field. Secondary refining process                             Processes which go beyond the primary distillation of crude oil into its component fractions. Seconds Saybolt Unit of measurement of oil viscosity mainly used in commercial specifications.       Section of Land (US)   One square mile, as defined for leasing purposes. Sedimentary basin/sedimentary rocks An area which in past geological era has been depressed, acquiring deposits of sedimentary rocks such as sands, silts or limestones.  These are formed from detritus or erosion etc of exposed formations and deposited in land or seabed depressions or as eg wind-formed desert dunes.  See also eg Alluvial Fan. Seismic obligation   A seismic survey committed to in winning award of a concession. Seismic survey       The collection of stratigraphic data obtained by creating shockwaves through the rock strata. Reflection of these waves from anomalies within the earths surface are electronically recorded at surface. These recordings are then analysed to produce a stratigraphic representation of the surveyed area. Self Potential/SP Log   See Log Semi-submersible rig A floating platform moored on location by anchors to the sea bed.  Stability in the water is achieved by submerged pontoons.  The latest models have been designed to operate in water depths of up to 1,500 feet (450 metres) although most of the existing generations are limited to nearer 500 to 600 feet (150-180 metres). Send-out    The quantity of gas delivered by a plant or system during a specified period of time. Separators        Processing equipment which splits the wellhead fluid into separate oil, water and gas streams. Service Factor   The proportion of time available during which a piece of equipment or whole installation is, or can be expected to be, fully effective.  Ineffective time or “downtime” may be due to weather, maintenance needs etc. Service/Supply Base The port installation from which an offshore drilling or production operation is maintained. Service Well   See Injection Well Set Back/Pick Up   Tubulars removed from a well are “set back” in the racks (see Tubing Board), and “picked up” for re-running into the well. Setting Point (Casing) The depth to which a string of casing is set and cemented. Seven Sisters   The seven most influential oil companies in the development of oil as a major force in world politics, namely BP, Gulf, Royal Dutch/Shell, Standard Oil New Jersey (Exxon), Standard Oil California (Chevron), Standard Oil New York (Mobil) and Texaco. Severance Tax A production tax in some areas of the USA. Shale/Shale Oil   Very fine-grained “muddy” sedimentary rock with low porosity and consequent poor reservoir potential.  Oil Shales or     Kerogen Shales contain Bituminous deposits which if found at the surface can be extracted by heating (Shale Oil). Shale Shakers See Mud.  Screens for extracting rock cuttings from circulating drilling mud. Ship-to-Ship transfer (STS) The transfer of crude oil or products from one ship to another while both are at sea. Ship or Pay (SOP)           In hydrocarbon transportation agreements, the obligation to pay for the transportation of an agreed minimum quantity per year. It ensures payment of the reserve capacity of the system whether it is used or not (usually called “Take or Pay”).  Shoe                      The strengthened fitting on the lower end of a string of casing to protect the tubulars and help direct the cement to the annulus. Shoestring Sand  Thin often elongated streaks of reservoir sand completely surrounded by impermeable layers. Short Trip   A trip during which the drill string does not reach the surface.  It may, for instance, be withdrawn from down hole into previously set casing for protection. Shotgun Tank   A tall, narrow separator column used in onshore “stripper” production. Shotpoint   See Seismic survey. Shut-in field Any field brought onstream which is not currently producing. Shut-in pressure   The pressure in a shut-in well; static pressure. Sialic Layer                      The upper layer of the earth’s crust, in which prospective reservoirs are found, so called from the predominance of Silicon and Aluminium in its composition. Sidescan Sonar   Acoustic survey equipment towed close to the seabed, used for surveying pipelines – see Sonar. Side-Track/Side-Tracked Well A well re-drilled from an intermediate depth.  Wells are re-directed or sidetracked for various reasons but usually because of technical problems deeper in the original well. Sidewall Coring   Obtaining rock samples from the sides of a well bore using a special tool. Signalling Pig   see Pig Single Anchor Leg Mooring (SALM)                          A compliant monopod version of the SBM tanker-loading buoy, used in deeper water.  (see Single Buoy Mooring) Single Buoy Mooring (SBM/SPBM)                         A single-point buoy mooring for loading and unloading tankers.  The oil is fed to or from the centre of the SBM from below, and the mooring gear and loading hoses can swivel above the buoy through a full circuit.  The tanker moors bows-on, and “weathervanes” around the buoy, presenting the minimum frontal area to the combined forces of wind and sea. Sitting on a well   This usually describes the role of the well-site geologist. Situation - Complication - Resolution Statement A logic framework that assists both in framing the idea and communicating the solution - especially useful to assist in arriving at the "day 1" answer Sizing Pig   See Pig Skidding the rig   Moving the derrick to a position above another wellhead or “slot” where a well is to be drilled or worked over etc. Skimmer   Equipment for removing a surface alyer of oil from an oil spill, or from an effluent water separator tank designed for the purpose. Skin factor An expression representing the effects on production well pressures and flows of eg formation damage. Slant drilling/slant rig                           Drilling a well from a non- vertical surface position.  Used offshore to reach distance parts of shallow reservoirs where depth is insufficient for normal deviated drilling. Slim –Hole drilling   Reducing the cost of a well, where technically feasible, by the use of specifically designed smaller diameter equipment.       Sling/Pipe Sling   A wire or rubber and fabric strop used in lifting tubulars. Slips   Metal wedges which are “set” in the annulus at the drilling floor to grip and support tubulars while sections are added or removed. Slop tank       Temporary storage for oil-contaminated water. Sloughing Crumbling or disintegration of the wall of a borehole. Slug/slug catcher        An accumulation of liquid eg condensed water, in a low point of a gas pipeline.  Slugs tend to accumulate when flow rate is low or interrupted. A slug catcher is a large separator for removing the slug at its destination without disrupting the gas flow. Slurry                1. A mix of cement and water used in drilling/cementing  2. Solid particles or crushed fragments in a liquid for pipeline transportation. Smoke point   A part of the specification for JP Fuels. Snubbers Tackle for exerting a downward force on a string of tubulars when inserting it into a well against very high pressures. SOFC Solid oxide fuel cell. Solid Alkanes   Hydrocarbon fractions which are solid at normal temperatures. Sole Risk   A provision in Joint Ventures whereby the only participant wishing to incur the costs of an activity eg drilling a well, may, under certain conditions, proceed with the well at its own cost, and thereby secure enhanced rights to any oil or gas found.  Sole risk development is also theoretically possible but very rare. Solution gas Natural gas which is dissolved in the crude oil within the reservoir. Solvent Common name for a liquid which is capable of dissolving or dispersing other substances. Solvent extraction  A refinery process where a solvent is used selectively to isolate and remove part of the process flow. Sonar          “Sound and Ranging”.  The use of sound echoes to locate objects underwater. Soup   Nitro-glycerine.  It is used in explosive fracturing of a down hole formation. Source rocks      The majority of evidence leads to the conclusion that hydrocarbons originated from the organic matter of muddy sediments deposited in depressions in the sea floor where the water was stagnant and lacking in oxygen.  Frequently these are clays or shales and such sediments are known as source rocks. Sour oil/gas   Oil or gas with a relatively high content of (odorous, poisonous or corrosive) sulphur compounds such as Hydrogen Sulphide. Sour gas is usually treated with triethanolamine to remove the unwanted elements. Source rock   The sediment/rock in which fossil deposits are formed into hydrocarbons which may then migrate into different porous formations.  See also Kitchen. SOx Sulphur oxides. SPACE        Computer programme which produces an expectation curve of recoverable hydrocarbons, using Monte Carlo techniques. This is the successor to PAQC and PADE and includes access to a global data base (as PAQC does). Spacing pattering The density of development drilling on a reservoir, expressed in acres per producing well. S.P.A.R.                      A very large manned SBM incoprorating oil storage. Sparker   Part of an echosounder for gauging the  thickness of soft seabed deposits. Spear   A “fishing” tool for recovering downhole tubulars by penetrating and gripping them from the inside. Specific Gravity The ratio of the density of a substance at a particular temperature to the density of water at 4øC. Spider                          A power-operated set of slips for gripping tubulars. Spider Deck   The lowest deck on an offshore drilling rig, below the rig floor. Spider Diagram                       A chart showing the sensitivity of a project’s NPV (or other economic indicator such as VIR) to variations in one parameter at a time. Spinner   A powered spanner or wrench for gripping and rotating drill pipe when screwing or unscrewing the joints. Previously the “spinning chain” was wrapped around each joint in turn and pulled on the cathead (winch) to rotate it. Splash Zone   The part of an offshore structure which is regularly exposed alternatively to atmosphere and water or spray and is consequently highly prone to sale and rust corrosion. SPM See SBM. Spool/spool piece   A short section of pipe with flanges or thread-connections at each end thus appearing “spool shaped”.  It may be of any length required to make up pipeline or casing to an exact required length. Spot charter A one-voyage tanker charter or one-well rig charter, as opposed to a time-charter. Spot market  An international market in which oil or oil products are traded for immediate delivery at the current price (the 'spot price'). Spotting   Placing cement etc accurately at a certain lvel in a well. Spread                      This has come to mean any complete set of equipment and ancillary vessels or vehicles, for a designated task eg pipelaying spread, diving spread. Spud   To start drilling a new well (or re-start) Spud can                           The end of each leg of a jack up rig or platform designed to penetrate the seabed and give a firm foundation for operations. Spur lines generally small diameter pipelines connecting a production facility to either a terminal platform or to a main pipeline leading to the shore. Squeeze                          Inserting cement under pressure into the poorly sealed annulus of a well, past the existing material. Squib Shot   An explosion set off in a producing well to stimulate production.  See Stimulation and Soup. Stab/Stabbing Board   To make a connection: to insert one device into another eg one stand of drillpipe into the string in the hole. To do this the derrick-man stands on the Stabbing Board high in the derrick. Stabilizer   1.  A distillation column for stabilizing crude oil Part of a drill-string, a tool with external things to give rigidity to the string  3. External fins on the hulls of shipping to minimise motion due to the sea  4. One of the columns or “legs” of a semi-submersible rig, which contains ballast compartments for stabilizing motion. Stabilized crude oil   Crude oil from which gases volatile at normal surface conditions have been removed, meeting commercial sale specifications. Stabilized well   A well in which the formation pressure is balanced by the weight  of the mud column in the well. Stack       1.  A vertical vent, chimney or flare  2. The  process of laying up an out-of-work rig or other equipment  3. A compilation of seismic signals in the processing of survey data. Standby rig rate        The daily charter rate for a rig in readiness but not incurring drilling costs. Stand of pipe   A short length of drill pipe pre-assembled to save time in operations and stored vertically in the derrick ready for use, usually in lengths of three joints or “Thribbles”, “Fourbles” and “Twobles” are also known. Standpipe      The fixed pipe taking mud from the mud pumps under pressure, up to the level of the rotary hose and swivel. Start up          The process of introducing feedstock to commissioned and tested plant and working it up to production capacity and efficiency. Steam injection/steam flooding Techniques used to lower the viscosity of residual oil in the reservoir and assist it to flow to a well.  See also Enhanced Oil Recovery. Stenching The process whereby odourless natural gas is given a smell for safety reasons by injecting small quantities of organic sulphur compounds, typically at the rate of 30 ppm. See also odorant. Step out well An appraisal well, specifically aimed at locating the lateral limits of the reservoir discovered. Sticking   Jamming of the drill string in the well borehole caused usually by a high differential pressure and a build- up of mud solids on the rock face. Still   A primitive distillation unit. Stimulation Methods such as acidizing (chemical) or fracturing (pressure) or explosions designed to break up “tight” low permeability reservoir rock in the vicinity of a well so that oil can flow freely into the bore. Stinger   In offshore pipelaying, the long submerged ramp which supports the length of recently welded pipe curving between the pipe lay-barge and the seabed, thus avoiding undue stressing, deformation or even the collapse of the pipe. Stock tank oil   Stabilized crude oil Stopcocking           Intermittent production from nearly exhausted or low-productivity wells, to allow time for pressure to build up while shut in. Stoppel A temporary plug inserted in a pipeline under repair. Storage facilities      For natural gas, these fall naturally into two categories, according to the IEA. The first is seasonal storage sites, which comprise aquifers (including depleted oil and gasfields); salt caverns; mined caverns; and disused mines. For peak storage, gasholders - originally used to store town gas - and linepacking are used. In addition, LNG storage tanks exist for either baseload or peak-shaving duties, depending on the market. of organic sulphur compounds, typically at the rate of 30 ppm. See also odorant. Storm choke In a producing well, an automatic down hole valve which closes with excessive flow rate or pressure drop.  An emergency safety valve. Stovepipe pipelaying On-site assembly of lengths of pipe, normally by welding.  Straddle packer                       A rubber packer or seal isolating a section of a well for production testing of the formation in question. Straight-Line Depreciation A scheme in which assets are depreciated in equal amounts over a number of years. Straight-run A description applied to a product of crude oil that has been made by distillation with no chemical conversion. Strake, Helical                        A spiral external fin to strengthen a stack. Strapping   The process of calibrating a storage tank for measurement of its contents.  Strata                          (Stratum)/stratigraphy Originally  predominantly horizontal layers of rock of a homogeneous type such as sedimentary deposits.  Subsequent local geological events may have tilted, rotated, folded or even inverted strata.                  Stratigraphy          is the pattern of succession of rock strata in an area, represented diagrammatically by a Stratigraphic or geological column. Stratigraphic trap                       is a structure where the “trap” is provided by layers of impermeable but possibly homogeneous rock rather than the geometrical “shape” of the rock formation.  They are consequently difficult to identify at the exploration stage. Strategy Table A structured approach to determining which strategy options overlap for various decision alternatives Stratigraphic traps                       occur where sedimentary layers have changed in characteristic.  For instance a deposit of coarse sand near shore may given place to finer grained sediment in deeper water and as these will vary in permeability an apparently isolated reservoir can occur. Another case would be where a sand layer wedges out onto an impermeable clay or shale and becomes isolated from its own sedimentary layer.  The latter type of trap is sometimes known as a pinch-out trap. Stream   The general flow of hydrocarbons from reservoir to finished product.  Processes relatively earlier in sequence are described as “upstream” and later “downstream: ie a refinery is upstream of a filling station but downstream of a production well.  However, all the extractive activities preceding shipment of stabilized crude oil or sales gas are collectively known as “upstream”, and a company operating only in these activities is known as an “upstream company”.  See also Onstream and Stream Day. Stream day                     A day when plan is onstream, excluding planned downtime etc.  Used in expressing plant throughput capacity (eg 50,000 barrels per stream day). Streamer                         A long cable towed behind a survey ship carrying hydrophones for receiving seismic survey or sonar signals. Strike                           1.  The angle of dip or inclination from the horizontal of rock stratum  2.  A strike is also a term for a discovery well. String   See Joint, Drill-string, Casing etc.  Any number of connected joints of tubulars run in the well. Stringer bead or pass   See Bead. Stripping: stripper well                           A nearly exhausted well, normally defined as having production of less than 10 barrels per day. Structure                     1.  A geological formation which, if sealed against leakage, could be a potential structural or stratigraphic trip for hydrocarbons 2.  A man-made load-  bearing construction such as an offshore platform, usually designed by structural engineers. Structural trap  A structure such as an anticline or fault- block in which a volume of reservoir rock is sealed above and on all sides by impermeable strata and/or faults. Stuck pipe   See Sticking Sub          1. A non-standard fitting of adaptor A sub-assembly A component tool in a drilling string. Submersible     A manned or remotely control vessel designed to operate completely submerged.  Sub sea enclosure  A sealed subsea chamber installed  over eg a subsea wellhead, providing access to it in normal surface atmospheric conditions. Sub-sea wellheads            In certain circumstances it is expedient to install a sub-sea wellhead to drain all or part of a deposit.  These are essentially wells drilled from a mobile drilling rig and completed with a series of valves and blow-out preventers on the sea bed.  This wellhead equipment is then connected to a central collecting area (either a platform, or a semi-submersible rig) by flexible or rigid pipelines.  If the wellhead equipment remains exposed to the sea it is called a wet-tree, but if it is encapsulated in a chamber under atmospheric pressure, it is a  dry-tree. Sub surface safety valve         A strong choke type valve installed in a development well, designed to seal the well in emergency until surface control has been resorted.  Also known as “Down-hole Safety Valve”. Success Ratio   The proportion of exploration wells which encounter significant hydrocarbons.      Commercial success ratio       is the smaller proportion encountering reservoirs of development potential. Super port   A port capable of accepting supertankers for loading or unloading. Superstructure   The deck, modules, and other parts of an offshore platform installed on the jacket or leg-section. Sometimes referred to as the “Top-sides”. Supertanker   A colloquial term for Very Large and Ultra Large Crude Carriers.  See ULCC and VLCC. Supply boat/ship/vessel   Vessels specially designed to carry loads to offshore installations and participate in loading/unloading by crane (or hose for water and fuels). They may also participate in eg anchor handling of the installation. They are highly manoeuvrable and robust. Surface string   See Casing. Surfactant A detergent or emulsifier, various of which are used in the oil industry.  Surfactants are increasingly used injected ahead of water in a waterflood system to overcome by capillary action the forces whereby the oil adheres to the rock grains. Surge tank   A vessel, provided at points in a pipeline or other flowline to accommodate temporary “surges” in pressure/fluid volumes due to timing differences in the opening or closing of valves, operation of pumps etc at either end of its section of line. Surveyor’s transit   A Theodolite. Survival capsule     A type of totally enclosed “life boat” used on some oil and gas installations.  See Brucker Capsule etc. Suspended well      A well, usually a successful discovery well, which is left temporarily sealed or plugged to be re- entered for further testing or for production purposes.   Sustainable development The meeting of present needs without compromising the ability of future generations to meet their own needs. Swabbing 1. Reducing pressure in a well to clean or stimulate it (or inadvertently)  2. Colloquially, to obtain information from someone. Swage Nipple                      An adaptor for connecting tubulars of different diameters. Sweetening See Sour oils. Sweet gas Natural gas containing very small amounts of hydrogen sulphide gas and carbon dioxide. Sweet gas reduces sulphur dioxide emissions into the atmosphere. Swing                     The amount by which the rate of gas to be supplied under a contract at any one time may differ from the daily contracted quantity at the buyer's choice. Swivel   The rotary bearing from which the kelly and drill string are suspended. Syncline A geological formation “opposite” in shape to an anticline eg saucer-shaped with the edges higher than the centre.  Although on a local scale synclines provide poor structural traps for hydrocarbons, on the larger scale of a sedimentary basin or sub-basin they are prime exploration areas. Synthetic gas                      Methane-rich gas manufactured from oil or coal that has the same basic characteristics and chemical composition as natural gas. After treatment to remove carbon dioxide, it is suitable as low-calorific town gas. T Tail ends  Overlaps in the distillation characteristics of oil fractions resulting in a mixture of the products in that  vaporisation range.  Tail gas   Residual gas from a refinery or other processing unit. Take-or-pay A contractual clause obliging a gas buyer to pay the seller for a contracted amount of gas in a fixed period, whether or not he takes physical delivery of it. Tank bottoms   Fluid in a tank below the pump suction/outlet, not normally evacuated. Tank dipping   The initial action in determining the contents of storage tanks.  A prepared weighted line is lowered through a “well” in the roof of the tank, and the level of the contents and/or underlying water marked. The volume represented by the difference in level is then calculated by reference to tank tables. Tanker   Any mobile storage unit for the bulk transport of crude oil, gas or products (eg road tanker, rail tanker) but normally refers to marine transport. Tank farm   An area at a refinery, terminal or storage depot dedicated to storage tanks and their safety requirements for surrounding space and spillage containment devices (see Bund Walls). Tank tables   The result of strapping a tank.  Calibration tables for an individual storage tank by the use of which the depth revealed in tank-dipping or gauging can be converted to a volume of contents. Taper mill   A pointed or tapered bit for cutting through tubular steel junk in a well.  Taper tap   A fishing tool similar in design to a normal taper tap.  It is screwed into the upper end of a tubular “fish” to enable recovery to the surface. Tapping a line   Cutting into a pipeline to install a branch connection.  See also Hot Tap. Tar   See Asphalt. Tariff   Any volume-based or tonnage-based rental charge for the use of an installation of equipment eg pipeline tariff, processing tariff.  As distinct from royalties tariffs are payable to the owners of the installation. Tar sands       Mixture of sand, water and heavy hydrocarbons; a   potential  alternative  source  of hydrocarbons. Tax Factor Can be used in-place of rigorous earnings and taxation calculations to calculate the after-tax values of both revenue and cost inputs. The expression of a given sum of money in a given year as an amount with equivalent purchasing power in the Reference Year. TCF  Trillion (1012) cubic feet. T/D Tonnes per day. TD   Total depth of a well. Tectonics   The process of formation and evolution of the earth’s solid surface crust.  “Plate tectonics” relates to the formation and movement of the “plates” of which the crust is composed. Telemetry   Remote instrumentation systems, so that for instance subsea well or satellite development platform temperatures, pressures etc can be read and recorded centrally. Temperature bomb A capsule containing instruments for measuring temperature down a well. Template     This usually refers to a structural framework within which subsea wellheads are grouped.  It may also refer to a prepared foundation or “mattress” for soft or shifting seabed on which a jackup rig etc can be stably installed.  Tensioners  Various types of device to maintain  controlled tension on a marine riser or one of the “tethers” of a tension-leg platform. Tension Leg Platform (TLP)         A semi-submersible platform which is moored or “tethered” vertically to anchor points on the seabed.  After tethering, the platform is deballasted to allow its buoyancy to place the tethers under pre-determined tension.  This has the effect of eliminating vertical “heave” of the platform but allowing some lateral compliance with sea forces.  Its main advantages are adaptability to increasing depth, minimal offshore “hook-up” work and ease of removal, at some cost in load-bearing potential compared with a fixed structure. Terajoule or TJ One trillion (1012) joules. Terminal This usually refers to a loading or unloading facility in a transportation system for oil or gas eg pipeline-to-tanker, tanker-to-refinery, trunk pipeline-to- distribution pipelines, pipeline-to-rail tanker, refinery-to- road tanker.  The term also covers associated processing and storage facilities. Tertiary recovery is a recovery method used to remove additional hydrocarbons after secondary recovery methods have been applied to a reservoir.  Sometimes more hydro- carbons can be removed by injecting liquids or gases (usually different from those used in secondary recovery and applied with different techniques) into the reservoir  Terminal An onshore transit installation that receives and stores crude oil and products from offshore production facilities via pipeline and / or tankers. Testing   See Drill stem testing, Hydrostatic testing, Non- Destructive testing, Well testing etc. Tethered Platform   A variant of the tension-leg platform. Thermal cracking                         A refinery process whereby the larger, heavier molecules in crude oil or its residue are broken down into lighter products by heating under pressure. Thermal recovery                       Enhanced Oil Recovery based on heating the oil in the reservoir by steam injection or sub- surface combustion (fire flood). Thief A device for taking samples of fluid from  intermediate levels in a storage tank consisting o fa small container on a line with a remotely controlled inlet.  It is inserted through the "thief hatch” in the tank roof. Thief zone   A porous, fractured or vuggy formation in a well, into which drilling fluid escapes.  It must be plugged or lined with casing. Third-party access (TPA)                         A TPA regime obliges companies operating gas transmission or distribution networks to offer terms for the carriage of gas on their systems by other gas distribution companies or particular consumers. Thixotrophy  The quality of fluids such as drilling mud and some clays to set when left undisturbed but to become fluid again when force or pressure is applied. This can be important in selecting eg jack up drilling sites as well as in mud engineering. Thread protector   A cape which is fitted over the ends of casing, tubing etc when not in use to protect the connections from damage and corrosion. Through flow line (TFL)   A system for inserting workover tools or instruments into a subsea well completion through the production gathering line or flowline. Thrusters   Fixed or “steerable” (direction or azimuth) propellers on a vessel which enable it to be manoeuvred with great accuracy. Thumper   See Vibrator: Vibroseis Tie-in   The action of connecting one pipeline to another or to equipment.  Hence “pipeline tie in” commonly describes the connection itself. Tight hole   1. A well regarding which information is restricted as highly confidential, usually in a competitive situation.  Communication is frequently in code  2. Occasionally used to describe a well from which production is restricted by low permeability or “tight” rock in the reservoir formation. Time charter   Rental of a rig or vessel, based on a rate for more than one voyage or well etc. Time map   A contoured map of a subsurface geological formation based on the time taken to reflect seismic impulses                  rather      than      the      subsequently computed/interpreted depths on a depth map. Tongs                      Tools for gripping and turning tubulars when making up or breaking out joints.  Now frequently power operated. Tonne A metric tonne is 1000 kg (2205 pounds), a long ton is 2240 pounds, a short ton 2000 pounds.  Tonnes of coal equivalent (TCE)             A method of assessing the work or calorific value of different sources of energy in terms pertaining to one tonne of coal. Tonnes of oil equivalent (TOE) A method of assessing the work or calorific value of different sources of energy in terms pertaining to one tonne of oil. Toolpusher The chief engineer of a drilling crew, with overall responsibility for the rig in the field. Topped crude Crude oil from which the light fractions (naphtha and lighter) have been distilled off in a “Topping Plant”. Torque     The turning force applied to any rotation eg rotary drilling, making up casing, tightening flange bolts etc.  Total Depth (T.D.) 1. The target depth for a well  2.  The achieved (drilled) depth in a well at any one time. Tour   1.  Drilling or other shift – usually 12 hours  2.  Any longer period of duty, such as say, 2 weeks offshore, or a period of assignment to a remote or foreign location. Tour sheet   The log of a drilling shift with details of all operations, materials and equipment used, and conditions encountered in the well.  Pronounced “Tower Sheet”. Town gas Gas piped to consumers from a gas plant. It can comprise manufactured gas, as well as natural gas for enrichment. Tornado Diagram A method of presenting the range of uncertainties on key variables and their priority. Tracing A system of steam pipes or electric elements fitted to vessels or pipelines to keep them warm so that very heavy viscous crude oil, for instance, will flow freely. Transducer An instrument for converting one form of energy into another – for instance enabling acoustic signals to be used in controlling a subsea well. Transmission The transport of large quantities of gas at high pressures, often through national or regional transmission systems. From the latter, gas is transferred into local distribution centres, for supply to customers, at lower pressures. Transmission pipeline         A    network  of   pipelines distributing natural gas from an onshore station, via compressor stations, to storage centres or distribution points. Transponder An acoustic device which on receiving a pre-set acoustic signal, transmits a response.  When fitted to a subsea wellhead, for example, this enables a rig to position itself very accurately for drilling or re-entry. Trap A geological structure in which hydrocarbons build up to form an oil or gas field. See also: structural trap. Travelling block The pulley block suspended from the crown block of a drilling rig, from which the hooks and swivel are in turn suspended. Tray   One of a series of perforated horizontal partitions in a distillation column designed to condense and draw off specific fractions of rising hydrocarbon vapour. Trillion   The Oil and Gas industry commonly uses the US definition, namely one million million 1012    (TCF – Trillion Cubic Feet). Trip   See Round Trip and Short Trip. Trip gas     High pressure gas in a well which must be carefully controlled when withdrawing the drill string (making a trip).    True Vertical Depth (TVD) The vertical distance below  surface datum reached by a deviated well. Trunk lines                       Long distance pipelines, as distinct from field, gathering or branch lines. Tubing/tubing head                           Wells are normally produced through tubing which is installed inside the casing in a well.  The              tubing head , similar to the casing head, is installed at the wellhead on the production tubing, seals off the annulus between casing and tubing, and carries the connections for production flowlines.  This assembly incorporates a tubing hangar similar to a casing hangar. Tubing board   See Derrick.  Tubulars   Covers all oilfield tubular materials but  primarily drill pipe, casing and production tubing. Turbine flowmeter                        An instrument which measures rates of flow in a pipeline by the electric current generated by a small rotor inserted in the line. Turnaround The process of completely overhauling a refinery, or piece of equipment.  A refinery will undergo a  shutdown and a turnaround every few years.  Turnaround is also the time taken to receive, load or unload and release a tanker of any kind. Turnkey contract  A fixed price contract for  Underwater Habitat   An air chamber or structure such   construction, drilling a well etc with the contractor taking risk of non-completion.  A true “turnkey” involves the contractor funding the operation until startup. Turret moored production facility                        In this design, a production turret (a cylindrical buoy) is built into a cavity similar to a moon-pool in a floating ship-shaped production facility.  The turret is connected to subsea wellheads by flexible hoses, and is moored in a fixed orientation.  The ship/facility, containing process storage and offloading equipment, is free to rotate or “weathervane” around the turret to present an optimum profile to wind and sea. TVD   (True vertical depth).  The linear distance measured perpendicular between an imaginary horizontal line drawn through a well surface location and any subsequent measured depth point. Twist of                        Severing of the drill pipe due to fatigue or excessive torque. T/Y tonnes a year. U UKCS United Kingdom Continental Shelf. ULCC   Ultra large crude carrier. An extremely large ocean-going tanker, over 300,000 metric tonnes dwt, used to transport crude oil. Ullage The space in a tank not occupied by its contents. Used as a measure of storage space still available. Ultimate Cash Surplus                        The value of the cumulative cashflow at the end of the project life. Ultra large crude carrier (ULCC) A crude oil tanker, often defined as having a deadweight tonnage or cargo capacity of 350,000 tonnes or more. Ultrasonic testing   A non-destructive testing method in which ultrasonic waves – (sound waves of frequencies too  Unassociated gas  See Associated Gas.  Unbundling The separation of the gas transport, storage and merchandising functions. Unconformity trap     This type of trap occurs when a series of rocks are deformed and raised above sea level and then eroded away.  When once again depressed below sea level the truncated ends are covered and sealed by horizontal beds which, if impermeable, provide a cap for any hydrocarbon accumulations which form in the truncated layers. Underlift        A situation where a participant in a joint production venture fails to take its full share of production   agreed limits of overlift/underlift necessary with eg periodic tanker shipments, oil underlifted may be deemed to be forfeited or “left in the ground” for pro rata benefit of all.  These provisions are intended to prevent any participant using joint storage to maximise profit on market fluctuations, to the detriment of others.  See Lifting.  Under-reamer A rotary drilling bit which can be  expanded downhole to enlarge the well bore.  See also Reamer.  as a diving bell in which divers etc can live while not working, or a chamber where work can be carried out such as subsea enclosure or hyperbaric welding chamber. Unit/Production Unit etc                When a reservoir is discovered to extend into more than one concession or licence area, it is common for the participants in the areas concerned to negotiate a mutual development, sharing all costs and production in proportion to the hydrocarbons in place or reserves in each area.  The participant with the largest equity share in the combined Unit is usually selected as  Unit Operator to undertake the common development and the negotiated basis of operations is the Unit Agreement , a form of Joint Operating Agreement which also normally provides for adjustment to participants shares if the reservoir is later found to underly the areas in different proportions from those initially assumed. Unitisation     occurs when stockholders of petroleum reserves pool their individual interests in return for an interest in the overall unit, which is then operated by one company on behalf of the group.  Unitisation leads to increased efficiency from maximising production and minimising development and producing costs. Universal Coupling   A joint which permits rotation from one shaft to be transmitted to another in a different plane. See, for instance, Knuckle Joint. Unsaturated Oil See Saturated Hydrocarbons, Fat Oil etc. Unstabilized Oil   See Stabilized Oil. Updip       An area of a structure where the top of the formation is higher (eg offshore, nearer sea level) than the point under consideration. Uplift     A fiscal device to compensate for the effect of inflation on depreciation. Upset   The thickening or increased diameter at the joints of tubulars to provide the necessary strength. Upstream    Those activities relating to the exploration, production and delivery to an export terminal of crude oil  V Vacuum distillation  Distillation of heavier fractions, at  a pressure well below atmospheric pressure and at accordingly reduced temperatures, thus saving fuel costs, and avoiding breakdown or “cracking” of the feedstock molecules. Value of Information Information is only valuable if it will influence the decision. The value of information is determined                 from     a      decision    tree      as: VOI = EMV (perfect information) - EMV (without perfect information). Vapour pressure The pressure exerted by the vapour from a substance, and also the pressure required to prevent a liquid from vaporising. Variable load   The operating load of equipment, fuel etc carried by a floating platform as distinct from its own unladen displacement.  Its capacity for variable load is similar to deadweight tonnage in a ship. Vertical integration                        In the oil industry, the process whereby an operating company amalgamates with operations further upstream and/or downstream (see Stream) in order to obtain greater commercial security by avoiding intermediate market fluctuations. Vertical Moored Platform   A tethered leg platform. Very large crude carrier – VLCC   Crude oil tanker with cargo capacity of around 175,000 dwt or over.  See also ULCC. Vibrating screen   A sieve-like part of the shale-shakers for separating rock cuttings and mud return from a well. Vibroseis/Vibrator   Onshore seismic survey based on a mobile vibrating energy source rather than on percussion. It is used where roads or terrain will accept the vehicles. Visbreaking   A refinery process for cracking and thereby reducing the viscosity of fuel oils. Viscosity/viscous Stickiness, i.e. the resistance that a liquid has to motion or flow; it normally falls as the temperature rises. Viscosity index A measure of the relationship between temperature and viscosity of an oil. Vitronite   See Kerogen VLCC   (Very large crude carrier) A large ocean-going tanker, over 200,000 metric tonnes dwt, used to transport crude oil. Volatile/volatility   The readiness with which a liquid converts to its gas state.  Highly volatile liquids include the “light” hydrocarbon fractions. Vortex flowmeter   An instrument for measuring flow- volumes based on the principle that a solid body in a flow stream sheds vortices with increasing frequency as flow speed increases. Vugs  Cavities in certain types of sedimentary rocks, often egg-sized or larger. Vulcanisation The cross-linking of polymer chains with sulphur to improve the characteristics of rubbery materials.  W Wall cleaner/scraper   See Scratchers     Washing-in a well       Cleaning a well by replacing the drilling mud with water or distillate. Wash out   Water leaks into the drilling mud downhole. Wash over A fishing tool which is designed to fit over the end of the “fish” before gripping it. Water-based mud   Drilling fluid based on suspension of solids such as Bentonites in water.  See also Oil based mud. Water Coning   See Coning. Water Drive         Where a hydrocarbon reservoir is in contact with an underlying water table, the formation pressure will “drive” the water into the rock pores vacated by produced fluids, thus tending to maintain reservoir pressure and assist production. Watered-out is when a production well is shut-in due to its unacceptably high proportion of water production. Waterflood is a method of secondary recovery in which water is injected into a reservoir in order to remove additional quantities of oil that would be left behind after primary recovery. Water injection               See Secondary Recovery and Waterflood. Watering out              When the proportion of water in production from a well is so high that it must be shut in. Water saturation   The proporation of water in the pore spaces of a reservoir.  See Porosity. Water separation               Removing the water from a production flow of oil or gas.  There are several techniques including settlement, heating and electrostatic precipitation particularly for breaking down water-oil emulsions. Water table    The level in the earth below which rock pores are saturated with water. Watt The basic unit of electrical power, defined as one joule per second. Wave period    The time separating successive crests of similar waves passing a given point. Wave recorder       An instrument which measures and records the height and frequency of waves. Wax            A solid or semi-solid material derived from petroleum distillates or residues; used for various purposes including candles and polishes. Weather window             The period of relatively good (summer) weather within which a given offshore operation can take place.  A weather window can also occur in winter, but is usually hard to predict and of short duration. Weathering          1. Permitting crude oil to stabilize by venting its volatile fractions to atmosphere (not now practised)  2. The process acting on exposed geological strata. Weevil An inexperienced and therefore accident-prone oilfield worker.    Weight indicator                      A large instrument on the rig floor which displays the weight of the drill string, and hence the pressure on the drilling bit. Weld fillet In welding overlapping surfaces, the weld makes a fillet in the angle formed by the end of the overlap. Welding bug                      Welding head of an automatic welding process. Well                           A hole drilled in rock from the surface to the reservoir in order to explore for, or extract, oil or gas. Well completion The process of equipping a well for development use as a producer, injector etc, eg casing, perforating, running tubing, fitting wellhead equipment etc.  The expression also covers the equipment installed. A well may for example be described thus:  “Type of completion – Upper Jurassic Producer”. Wellhead 1.  Descriptive of a location or function rather than a specific item of equipment  2. The control equipment fitted to the top of the well, consisting of outlets, valves, blowout preventers etc. See also: Christmas tree. Wellhead platform An offshore platform designed to support only wellheads and associated piping, production fluids being transferred to a shore gathering station or nearby platform for processing.  Sometimes called a Drilling Platform, if equipped with an integral rig and drilling facilities. Well permit                        Government permission to drill a well. Obtaining this is frequently a detailed process. Well program The engineering design and technical/ operational plan for drilling a well, completing and testing (as applicable). Well servicing                                  Bringing a completed well into production, and subsequent maintenance “workovers”. Well shooter   An explosives expert who uses downhole explosions to stimulate production. Well symbols   Conventional symbols used in mapping to show location and type of well. Well testing   Testing in an exploration or appraisal well is directed at estimating of reserves in communication with that well, in addition to well productivity. Testing in a production well also monitors the effects of cumulative production on the formation.  Tests basically consist of a series of measurements of pressures, fluid flows and temperatures down hole (PVT) in a controlled sequence of “flowing” and “shut-in” periods for recovery of stable reservoir conditions.  The time taken to recover is also recorded. Various forms of well stimulation may also be built into the sequence.  Tests will also include the functioning of well equipment. Wet gas   Natural hydrocarbon gas containing significant amounts of naturally liquid hydrocarbons. Wet tree   A subsea wellhead “tree” which is exposed to the water rather than enclosed. Wet weld Underwater welding as opposed to normal atmospheric welding or hyperbaric chamber welding. Whipstock   A tool for deviated drilling, basically a wedge- shaped block which is lowered into the well to divert the bit onto a chosen path at an angle to the original hole. Whitaker capsule   A type of survival capsule.       White oil/white cargo   Clean or distilled petroleum, or products not including heavy “black” residues nor crude oil. White products Gasoline, naphtha, kerosene and gas oil, i.e. products from the high or light end of the distillation process. See also: black products, light fractions. Wide cut      A product of crude oil distillation in which several fractions are combined usually at the heavy distillate/residual fuel oil end of the range. Wildcat    Refers to an exploration well drilled without complete geological knowledge of the locality. Wildcat well An exploratory well drilled without detailed knowledge of the underlying rock structure. Window mill     A downhole cutting tool used to cut an aperture laterally in the casing to sidetrack or deviate the well. Wireline logs Electrical devices run down a well on a steel cable.  The equipments response is used to determine rock lithology, permeability, porosity, formation fluid type, cement bond effectiveness, etc. Wobbe Index An expression of the heating value of a gas flame, used in gas marketing.  It is derived by dividing the gross calorific value of the fuel by the square root of its specific gravity, expressed in eg megajoules per cubic metre or BTU per cubic foot. W.O.C. Time   Time when a rig is “waiting on cement” to set. Working interest   A full “equity” interest in an oil or gas concession, as distinct from, for instance, a royalty entitlement or net profits interest. Workover         A maintenance job on a well usually to replace equipment or to stimulate production. Worldscale rates     A schedule of nominal freight rates against which tanker rates for all voyages, at all market levels, can be compared and readily judged. W.O.W. time   Time when a rig or installation vessel etc is “waiting on weather” to moderate before operations can continue. X Xaloy A low friction alloy used for facing drilling tools etc. Y Yield   The total amount of product of a refinery process or of all products of all processes of a refinery compared with the equivalent amount of feedstock.  A “Refinery Yield” for a given crude oil feedstock and refinery will include a table of amounts of all products derived from a barrel or tonne of crude minus the refinery’s own usage for fuel, flaring and other losses.  Since refineries commonly use several feedstocks simultaneously, such a yield is often measured or predicted on the basis of adding incremental feedstock to a fixed throughput.                                              Yield point   The force needed to start a fluid flowing i.e. to overcome its viscosity or thixotropy. Z Zeolytic catalyst                        A type of catalyst used in catalytic crackers. Zone                        1. The interval between two depths in a well containing a reservoir or other distinctive characteristics Specific areas where restrictions apply eg Safety zone (round offshore installation), Danger zone (military activity area) etc.     Standard Reference Fuels and Equivalents   Basic Energy Units   1 British Thermal Unit = 0.252 kcal= 1.055 kJ 1 kilocalorie= 3.968 Btu = 4.187 kJ 1 kilojoule= 0.948 Btu= 0.239 kcal 1 barrel oil equivalent= 5.8 million Btu  1 tonne oil equivalent = 10 million kcal 1 tonne coal equivalent = 7 million kcal 1 therm= 100,000 Btu  1 therm = 1000 kcal 1 kilowatt-hour= 3412 Btu = 3600 kJ