Glossary

1. ampere. 2. cross-sectional area, in.2 3. well spacing, acres.

1. a derrick or crane shaped like the letter A and used to handle heavy loads. 2. an A-shaped openwork structure that is the stationary and supporting component of the mast of a jackknife rig and to which the mast is anchored when it is in an upright or drilling position. 3. the uppermost section of a standard derrick, shaped like the letter A and used as a support in lifting objects such as the crown block to the water table. See gantry.

ampere-hour.

an A-shaped arrangement of upright poles, usually steel, used for lifting heavy loads. See A-frame.

antiagglomerant.

American Association of Petroleum Geologists.

American Association of Petroleum Land­men.

Association of American Railroads.

1. toward the stern of a ship or mobile offshore drilling rig. 2. behind. 3. farther aft than. See aft.

to cease producing oil and gas from a well when it becomes unprofitable or to cease further work on a newly drilled well when it proves not to contain profitable quantities of oil or gas. Several steps are involved: part of the casing may be removed and salvaged; one or more cement plugs are placed in the borehole to prevent migration of fluids between the different formations penetrated by the borehole; and the well is abandoned. In most oil-producing states, it is necessary to secure permission from official agencies before a well may be abandoned.

a well not in use because it was a dry hole originally, or because it has ceased to produce. Statutes and regulations in many states require the plugging of abandoned wells to prevent the seepage of oil, gas, or water from one stratum of underlying rock to another.

termination of a jurisdictional sale or service. Under Section 7(b) of the Natural Gas Act, the Federal Energy Regulatory Commission must determine in advance that the “present or future public convenience and necessity” or depletion of gas supplies requires termination.

the average reservoir pressure at which an amount of gas insufficient to permit continued economic operation of a producing gas well is expelled.

an old-style choke, which is no longer manufactured. A steel rod went through the center of a 2-in. (50.8-mm) pipe, which a rubber boot surrounded. Hydraulic pressure expanded the boot to close the choke. It tended to wear and fail in the full-open position.

abandoned; used in drilling reports.

to or at the side of a ship, vessel, or offshore drilling rig and especially at right angles to the ship, vessel, or rig’s length.

strictly speaking, pressure in a formation that is less than or more than the pressure to be expected at a given depth. However, in the field, abnormal pressure is often considered to be pressure only that is higher than that which is expected at a given depth. Normal pressure increases approximately 0.465 pounds per square inch per foot of depth or 10.5 kilopascals per metre of depth (this value may be slightly more or slightly less than 0.465 psi or 10.5 kilopascals, depending on a particular area). In general, however, normal formation pressure at 1,000 feet is 465 pounds per square inch; at 1,000 metres it is 10,500 kilopascals. See pressure gradient.

on or in a ship, offshore drilling rig, helicopter, or production platform.

wearing away by friction.

American Bureau of Shipping.

a one-time verification that a ship or other marine structure meets an ABS standard.

a process that occurs over the life of a vessel, ship, offshore rig, or other structure to ensure that such structures are not only built, but also maintained to ABS and industry-accepted standards.

the horizontal coordinate of a point in a plane obtained by measuring parallel to the x-axis. Compare ordinate.

independent or unlimited, such as an absolute condition, or completely unadulterated, such as alcohol.

the density of a solid or liquid substance at a specified temperature. Sometimes referred to as true density or density in vacuo. See density.

the force in dynes that a stationary flat plate with a surface area of 1 square centimetre exerts on a similar parallel plate 1 centimetre away and moving in its own plane with a velocity of 1 centimetre per second, the space between the plates being filled with the liquid in question. It is a measure of the resistance that the liquid offers to shear.

the difference between the result of a mea­surement and the true value of the measured quantity as determined by means of a suitable standard device.

the amount of moisture present in the air. It may be expressed in milligrams of water per cubic metre of air. Compare relative humidity.

the value obtained when the absolute dynamic viscosity is divided by the density (expressed in grams per cubic centi­metre) of the liquid at the temperature concerned.

the expression of a fluid’s weight (mass) in terms of its weight in a vacuum.

the maximum flow rate that a well could theoretically deliver with zero pressure at the face of the reservoir.

see absolute open flow.

the theory that minerals such as oil and gas are fully owned in place before they are extracted and reduced to possession. Despite this theory, title to oil and gas may be lost by legitimate drainage and by the rule of capture. Also called ownership in place. See rule of capture.

a measure of the ability of a single fluid (such as water, gas, or oil) to flow through a rock formation when the formation is totally filled (saturated) with that fluid. The permeability measure of a rock filled with a single fluid is different from the permeability measure of the same rock filled with two or more fluids. Compare effective permeability, relative permeability.

the percentage of the total bulk volume of a rock sample that is composed of pore spaces or voids. See porosity.

total pressure measured from an absolute vacuum. It equals the sum of the gauge pressure and the atmospheric pressure. Expressed in pounds per square inch absolute (psia).

a scale of temperature measurement in which zero degrees is absolute zero. On the Rankine absolute temperature scale, which is based on degrees Fahrenheit, water freezes at 492° and boils at 672°. On the Kelvin absolute temperature scale, which is based on degrees Celsius, water freezes at 273° and boils at 373°. See absolute zero temperature.

the property by which a fluid in motion offers resistance to shear and flow. Usually expressed as newton-seconds/metre.

defined as precisely 0°K on the Kelvin scale, −273.15°C on the Celsius scale, 0°R on the Rankine scale, and −459.67°F on the Fahrenheit scale.

a hypothetical temperature at which there is a total absence of heat. Since heat is a result of energy caused by molecular motion, there is no motion of molecules with respect to each other at absolute zero.

1. to take in and make part of an existing whole. 2. to recover liquid hydrocarbons from natural or refinery gas in a gas-absorption plant. The wet gas enters the absorber at the bottom and rises to the top, encountering a stream of absorption oil (a light oil) traveling downward over bubble-cap trays, valve trays, or sieve trays. The light oil removes, or absorbs, the heavier liquid hydrocarbons from the wet gas. See bubble-cap tray, sieve tray, valve tray.

see absorption oil.

1. a vertical, cylindrical vessel that recovers heavier hydrocarbons from a mixture of predom­in­antly lighter hydrocarbons. Also called absorption tower. 2. a vessel in which gas is dehydrated by being bubbled through glycol. See absorb.

the maximum volume of natural gas that can be pro­cessed through an absorber at a specified absorption oil rate, temperature, and pressure without exceeding pressure drop or any other operating limitation.

a system of gas dehydration using glycol desiccants. See contactor, glycol system.

1. the process of sucking up, taking in and making part of an existing whole. Compare adsorption. 2. the process in which shortwave radiation is retained by regions of the earth. 3. in gas treatment, the process in which liquid hydrocarbon molecules in the inlet gas are taken up (absorbed) and removed.

a device that measures mechanical force. The energy measured is absorbed by frictional or electrical resistance.

the gasoline extracted from natural gas by putting the gas into contact with oil in a vessel and subsequently distilling the gasoline from the heavier oil.

a hydrocarbon liquid used to absorb and recover components from natural gas being processed. Also called wash oil.

a plant that processes natural gas with absorption oil.

see absorber.

a mechanical refrigeration system in which the refrigerant is absorbed by a suitable liquid or solid. The most commonly used refrigerant is ammonia; the most commonly used absorbing medium is water. Compare compression-refrigeration cycle.

a private company in the business of preparing abstracts of title and performing related services. Also called abstract plant.

a collection of all of the recorded instruments affecting title to a tract of land. Compare base abstract.

see abstract company.

a title opinion based on a complete abstract of title and other relevant documents. Compare stand-up title opinion.

of or relating to the bottom waters of the ocean.

altocumulus.

alternating current.

in a diesel-electric power system, a common set of conductors made up of large, heavy-duty copper cables that carry alternating current generated by the system’s alternators (AC generators).

a procedure whereby a product may be subjected to intensified but controlled conditions of heat, pressure, radiation, or other variables to produce, in a short time, the effects of long-time storage or use under normal conditions.

the rate at which something increases in velocity with respect to time.

when a crane is hoisting a load, the additional force the load imposes on a wire rope or a sling when the load’s speed increases.

a chemical additive that reduces the setting time of cement. See cement, cementing materials.

instruments that detect changes in motion or measure acceleration and gravity-induced reaction forces.

a secondary part or assembly of parts which contributes to the overall function and usefulness of a machine.

any device that enhances the utility of a measurement system, including readouts, registers, monitors, and liquid- or flow-conditioning equipment.

to enlarge by the addition of external parts or particles.

to amass or collect. When oil and gas migrate into porous formations, the quantity collected is called an accumulation.

1. a vessel or tank that receives and temporarily stores a liquid used in a continuous process in a gas plant. See drip accumulator. 2. on a drilling rig, an assembly of devices such as bottles, control valves, pumps, and hydraulic fluid reservoirs that stores hydraulic fluid under pressure and provides a way for personnel to operate (open and close) the blowout preventers. Also called surge bottles. See blowout preventer, blowout preventer control unit.

a bottle-shaped steel cylinder located in a blowout preventer control unit to store nitrogen and hydraulic fluid under pressure (usually at 3,000 pounds per square inch). The fluid operates the blowout preventers. See blowout preventer control unit.

the ability of a measuring instrument to indicate values closely approximating the true value of the quantity measured.

a plot of meter factor as a function of flow rate used to evaluate the meter’s performance. See flow rate, meter factor.

an organic acid compound sometimes used to acidize oilwells. It is not as corrosive as other acids used in well treatments. Its chemical formula is C2H4O2, or CH3COOH.

a method of joining steel components in which acetylene gas and oxygen are mixed in a torch to attain the high temperatures necessary for welding. As an early type of welding (it was also called oxyacetylene welding), its primary disadvantage was the seepage of molten weld material onto the interior surface of the pipe, often leading to corrosion problems.

actual cubic feet per minute. Refers to the actual volume of gas supplied to a diver, bell, etc. at ambient pressure.

American Conference of Governmental and Industrial Hygienists.

1. any chemical compound, one element of which is hydrogen, that dissociates in solution to produce free hydrogen ions. For example, hydrochloric acid, HCl, dissociates in water to produce hydrogen ions, H+, and chloride ions, Cl–. This reaction is expressed chemically as HCl + H+ + Cl–. See ion. 2. a liquid solution having a pH of less than 7; a liquid acid solution turns blue litmus paper red.

see hydrogen embrittle­ment.

a naturally occurring clay that, after activation, usually with acid, is used mainly as a decolorant or refining agent, and sometimes as a desulfurizer, coagulant, or catalyst.

a characteristic of diesel fuel that indicates the likelihood of a diesel fuel’s causing corrosion as the engine burns fuel. In general, a fuel with a high acid content will be more corrosive than a fuel with low acid content.

to part or open fractures in productive hard limestone formations by using a combination of oil and acid or water and acid under high pressure. See formation fracturing.

see acid fracture.

a gas that forms an acid when mixed with water. In petroleum production and processing, the most common acid gases are hydrogen sulfide and carbon dioxide. Both cause corrosion, and hydrogen sulfide is very poisonous.

plant for the recovery of sulfuric acid from acid sludge.

material of high specific gravity formed during the chemical refining treatment of oils by sulfuric acid and usually separable by settling or centrifuging. Also called acid tar.

a well stimulation method using acid. See acidize.

see acid sludge.

a method by which petroleum-bearing limestone or other formations are put into contact with an acid to enlarge the pore spaces and passages through which the reservoir fluids flow.

an acid treatment in which an acid mixture is circulated through a well­bore to clean the perforations.

to fracture a well using acids (acidizing).

the quality of being acid. Relative acid strength of a liquid is measured by pH. A liquid with a pH below 7 is acid. See pH.

to treat oil-bearing limestone or other formations with acid for the purpose of increasing production. Hydrochloric or other acid is injected into the formation under pressure. The acid etches the rock, enlarging the pore spaces and passages through which the reservoir fluids flow. Acid also removes formation damage by dissolving material plugging the rock surrounding the wellbore. The acid is held under pressure for a period of time and then pumped out, after which the well is swabbed and put back into production. Chemical inhibitors combined with the acid prevent corrosion of the pipe.

see acidize.

a declaration or an avowal of any act or fact made by a signatory party to a document to a notary public or other public official authorized to take an acknowledgment to give it legal effect.

in offshore drilling from a floating drilling rig using a subsea blowout preventer stack, devices that send acoustic signals to a subsea receiver to operate the blowout preventer (BOP) components. The system consists of a miniature control pod with several subsea pilot manipulated (SPM) valves to operate the selected BOP components. The system is used when the hydraulically operated system fails.

the total reaction of a medium to the transmission of sound through it; acoustic impedance is often expressed as the ratio of sound pressure to particle velocity at a given point in the medium. Mathematically, the acoustic impedance (Z) of a material is defined as the product of its density (p) and its acoustic velocity (V), or Z = pV .

a record of the measurement of porosity, done by comparing depth to the time it takes for a sonic impulse to travel through a given length of formation. The rate of travel of the sound wave through a rock depends on the composition of the formation and the fluids it contains. Because the type of formation can be ascertained by other logs, and because sonic transit time varies with relative amounts of rock and fluid, porosity can usually be determined in this way.

a system consisting of a beacon positioned on the seafloor to transmit an acoustic signal, a set of three or four hydrophones mounted on the hull of a floating offshore drilling vessel to receive the signal, and a position display unit to track the relative positions of the rig and the drill site. Monitoring of the display unit aids in accurate positioning of the rig over the site.

the characteristic patterns for various degrees of cement bonding between the casing and the borehole that appear on an oscilloscope display when a sonic cement bond log is made.

a well-logging method in which sound impulses are generated and transmitted into the formations opposite the wellbore. The time it takes for the sound impulses to travel through the rock is measured and recorded. Subsequent interpretation of the record (log) permits estimation of the rock’s porosity and fluid content.

time required for a specific sound wave to travel from one point to another. Electric logs use acoustic travel time to determine characteristics of a formation.

the process of recording the acoustic characteristics of subsurface formations, based on the time required for a sound wave to travel a specific distance through rock. The rate of travel depends on the composition of the formation, its porosity, and its fluid content. Also called sonic logging.

land owned by the United States, acquired by deed or otherwise. Such land has never been in the public domain or was in the public domain at one time and was later reacquired by purchase, condemnation, or donation.

a unit of volume often used in oil reservoir analysis, equivalent to the volume (as of oil or water) necessary to cover 1 acre to a depth of 1 foot.

acre-foot.

acreage owned in the vicinity of a test well being drilled by another party and contributed to the driller of the well in return for information obtained from its drilling. The assignment of information is usually made on completion of the well.

over. The term usually relates conditions of fluid flow on one side of a piece of equipment to conditions on the opposite side (e.g., a pressure drop across a separator).

aluminum cable steel-reinforced conductor.

automatic custody transfer.

a form of carbon characterized by a high absorptive and adsorptive capacity for gases, vapors, and colloidal solids.

a reaction in which an element has been changed into an unstable isotope during bombardment by neutrons.

a hydraulic power assist device used to overcome friction of the passive heave compensator seal and the drill string that act in opposite direction to the motion of the ship. Such compensators are used onboard drillships and semisubmersible drilling rigs.

one of usually two, three, or more mud tanks that holds drilling mud that is being circulated into a borehole during drilling. They are called active tanks because they hold mud that is currently being circulated.

the sum of the ideal pressure and the dynamic pressure.

the volume of gas remaining after processing in a plant.

see breaking strength.

a device that activates or puts into motion a process or an action by use of pneumatic, hydraulic, or electronic signals; for example, a valve actuator opens or closes a valve.

1. a state or county tax based on the value of a property. 2. tax imposed at a percent of a value.

a kit comprising a setting sleeve, adapter rod, and adjustment nut for setting drillable or permanent tools on wireline or by using hydraulic setting tools.

a joint to connect blowout preventers of different sizes or pressure ratings to the casinghead.

one of a collection of numbers to be added.

1. in general, a substance added in small amounts to a larger amount of another substance to change some characteristic of the latter. In the oil industry, additives are used in lubricating oil, fuel, drilling mud, and cement. 2. in cementing, a substance added to cement to change its characteristics to satisfy specific conditions in the well. A cement additive may work as an accelerator, retarder, dispersant, or other reactant.

a force of attraction that causes molecules of one substance to cling to those of a different substance.

describing a process in which there is no transfer of heat into or out of the system in question.

a change in the volume, pressure, or temperature of a gas, occurring without a gain or loss of heat.

compression of air or gas that exists when no heat is transferred between the air or gas and surrounding bodies (such as the cylinders and pistons in a compressor). It is characterized by an increase in temperature during compression and a decrease in temperature during expansion.

the expansion of a gas, vapor, or liquid stream from a higher pressure to a lower pressure with no change in enthalpy of the stream.

a choke in which the position of a conical needle, sleeve, or plate may be changed with respect to their seat to vary the rate of flow; may be manual or automatic. See choke.

a part of a downhole motor assembly used to kick off or deflect the hole from vertical in a directional hole. The critical equipment is the adjustable kickoff sub (as opposed to fixed bent sub or bent housing). The kickoff angle can be set in an adjustable sub then pulled and reset without changing tools. It can be used to increase or to decrease hole angle. See bent housing.

a sub run below a dual or triple packer to permit the correct space-out. See space-out.

the operation of bringing a measuring instrument, such as a meter, into a satisfactory state of performance and accuracy.

penalties or fines handed down by administrative agencies, such as the EPA.

person appointed by the court to administer the estate of someone who dies without a will (intestate).

atmospheric diving system.

to adhere to a surface. See adsorption. Compare absorption.

a solid used to remove components from natural gas that is being processed.

the adhesion of a thin film of a gas or liquid to the surface of a solid. Liquid hydrocarbons are recovered from natural gas by passing the gas through activated charcoal, silica gel, or other solids, which extract the heavier hydro­carbons. Steam treatment of the solid removes the adsorbed hydrocarbons, which are then collected and recondensed. The adsorption process is also used to remove water vapor from air or natural gas. Compare absorption.

a plant that processes natural gas with an adsorbent.

in a gas processing facility, a vessel in which liquid hydrocarbons are removed from gaseous hydrocarbons by passing the hydrocarbon stream through a solid material to which the liquids adhere as the stream flows past the material. See adsorption.

an agreement between a producer and a purchaser to make an advance payment for gas to be delivered at a future date.

a fog caused by the movement of warm, moist air over a surface with a temperature less than the dew point of the air. Also called sea fog.

a method of asserting and gaining title to property against other claimants, including the owner of record. The claim through adverse possession must include certain acts (as required by statute) over an uninterrupted interval of time. It must also be, in most states, “open,” “notorious,” and “hostile.”

deposited by wind.

a sediment deposited by wind.

a rotary drilling method in which the circulated drilling fluid is a mixture of liquid and air or gas.

a drilling mud, usually water based, into which air or gas is injected to lighten the mud. Aerated drilling typically uses conventional mud pumps in conjunction with large auxiliary air compressors. The mud is pumped to the stand­pipe where high-pressure air is injected into the mud stream before it enters the drill stem. Aerated muds may be used in wells where it is not possible to drill with air or gas alone but it is possible to drill with lightweight mud. Using air, gas, or aerated mud increases the rate of penetration because the hydrostatic pressure of such fluids, being less than the hydrostatic pressure of liquid mud, does not tend to hold down the cuttings made by the bit. Thus, the drill cuttings easily move away from the bottom of the hole, which allows the bit to work on fresh, uncut formations. Aerated mud has higher cuttings carrying capacity than air or gas drilling.

see aerated drilling mud.

the injection of air or gas into a liquid. In the oil industry a common form of aeration is the injection of natural gas into reservoir liquids standing in a well. Aeration with natural gas reduces the density of the liquids and allows declining reservoir pressure to lift the liquids. See gas lift.

see air-cooled exchanger.

a river crossing technique in which a pipeline is either suspended by cables over a waterway or attached to the girders of a bridge designed to carry vehicular traffic.

requiring free atmospheric oxygen for normal activity.

bacteria that require free oxygen for their life processes. Aerobic bacteria can produce slime or scum, which accumulates on metal surfaces, causing oxygen-concentration cell corrosion.

suspension of very small particles in a gas.

Association of Energy Service Companies.

arc fault circuit interrupter.

authority for expenditure.

the person who makes a sworn statement.

a written affirmation of fact made and sworn to before a notary public or other authorized official. The official signs a certificate called a jurat, which states that the affidavit was signed and sworn to before him or her.

a company that is either directly or indirectly controlled and/or owned by another firm or company.

toward or near the stern of a ship or offshore drilling rig.

on a supercharged engine, a device, cooled by either air or by engine coolant, that reduces the temperature of the engine’s exhaust. It is necessary to cool the exhaust’s temperature because the exhaust drives the supercharger, which forces air into the engine’s intake manifold. The temperature of the supercharged air must be at an acceptable level; otherwise, the engine will run too hot. See supercharger.

(pronounced tower) see evening tour.

American Gas Association.

to allow cement to mature, or reach a stage harder than that of immediate setting. The process is sometimes called curing. See cure.

a federal entity such as a department, a bureau, a corporation, a com­mission, or a division under the U.S. government that is charged by Congress to administer, implement, and enforce U.S. law.

the surface owner given the right to grant an oil and gas lease, with the owner and state splitting any benefits from that lease.

the groups of larger individual particles usually originating in sieving or drying operations.

the grouping of individual particles.

a group of two or more particles held together by strong forces. Aggregates are stable with normal stirring, shaking, or handling; they may be broken by treatment such as ball milling a powder or shearing a suspension.

formation of aggregates. In drilling fluids, aggregation results in the stacking of the clay platelets face to face. The viscosity and gel strength decrease in consequence.

see accelerated aging test.

a motor-driven paddle or blade used to mix the liquids and solids in drilling mud.

anchor-handling tug/supply vessel.

anchor-handling tug/supply

anchor-handling vessel

anchor-handling vessel.

American Institute of Mining, Metallurgical, and Petroleum Engineers.

a colorless, odorless, tasteless, gaseous mixture, mainly nitrogen (approx­imately 78 percent) and oxygen (approximately 21 percent) with lesser amounts of argon, carbon dioxide, hydrogen, neon, helium, and other gases.

a special aeration unit that forces air into dry mud material (such as bentonite), and which assists crew members in transferring the dry material from a bulk tank on the rig to a transport truck.

a roller cone bit that is specially designed for air or gas drilling. It is very similar to a regular bit, but features screens over the bearings to protect them from clogging with cuttings and thicker hard­facing on the shirttail to protect them from abrasive, high-velocity air or gas drilling fluid.

a device installed on an engine’s air intake to remove foreign materials, such as dirt or dust, from the air before it enters the engine.

see air cleaner filter element.

the part of an engine’s air cleaner that traps dust and dirt particles in the intake air that passes through the element. Filter elements are designed to trap most, but not all, of the foreign material that may be in the air taken in by an engine. (If the filter elements trapped all particles, they would have to be replaced too frequently to be practical.) Some elements, after they become clogged with dust, can be cleaned and reused; others must be discarded and replaced.

diving in which a diver uses a normal atmospheric mixture of oxygen and nitrogen as a breathing medium. It is limited to depths less than 190 feet (58 metres) because of the dangers of nitrogen narcosis; however, dives with bottom times of 30 minutes or less may be conducted to a maximum of 220 feet (67 metres).

a method of rotary drilling that uses compressed air as the circulation medium. The conventional method of removing cuttings from the wellbore is to use a flow of water or drilling mud. Compressed air removes the cuttings with equal or greater efficiency. The rate of penetration is usually increased considerably when air drilling is used; however, a principal problem in air drilling is the penetration of formations containing water, since the entry of water into the system reduces the ability of the air to remove the cuttings.

a part of a LACT unit installed ahead of the metering equipment to separate and remove mass volumes of air and gas from the fluid.

the distance from the normal level of the sea surface to the bottom of the hull or base of an offshore drilling platform or rig.

1. a hand tool that is powered pneumatically. 2. a chamber filled with compressed air, often used offshore in seismic exploration. As the gun is trailed behind a boat, air is released, making a low-frequency popping noise, which penetrates the subsurface rock layers and is reflected by the layers. Sensitive hydrophones receive the reflections and transmit them to recording equipment on the boat.

a drilling tool that, when placed in the drill stem just above a special bit, delivers high frequency percussion blows to the rotating bit. Hammer drilling combines the basic features of rotary and cable-tool drilling (i.e., bit rotation and percussion).

a hoist operated by compressed air; a pneumatic hoist. Air hoists are often mounted on the rig floor and are used to lift joints of pipe and other heavy objects.

the network of devices by which air is taken into an engine for combustion in the cylinders.

1. the injection of air into a reservoir in a pressure maintenance or an in situ combustion project. 2. the injection of fuel into the combustion chamber of a diesel engine by means of a jet of compressed air.

on a diesel engine, an arrangement of pipes and passageways through which air is conducted to the engine’s combustion chambers.

on a diesel engine, a phenomenon that occurs when trapped air in the fuel injection system enters the engine’s cylinder with the fuel. The fuel-air mixture ignites but, because of the extra air in the fuel, the engine cylinder misfires and knocks or hammers. The problem should be corrected promptly to prevent damage to the engine.

a body of air that remains for an extended period of time over a large land or sea area with uniform heating and cooling properties. The air mass will acquire characteristics (such as temperature and moisture content) of the underlying region.

an area over which an air mass rests and develops temperature and moisture characteristics typical of that location.

a motor powered by compressed air.

on a diesel engine, a special valve that, when activated, prevents air from entering the engine’s combustion chambers, thereby stopping the engine. Air shut­off valves are a safety feature that may be needed when a well blows out. If natural gas is present in the blowout’s fluids, a diesel engine can take in the gas and continue to run even when its normal fuel source is cut off.

a mechanism using pressurized air through a diaphragm to fluidize powdered materials so that they will flow from a delivery truck to a storage tank on the rig site.

a clutch containing an inflatable tube that, when inflated, causes the clutch to engage the driven member. When the tube is deflated, disengagement occurs.

air winches that move heavy materials and position equipment to help set up the rig. See air hoist.

a device used to separate and remove gases from a liquid to be measured to prevent an error in liquid measurement.

equipment activated by compressed air, as are the clutch and the brake system in drilling equipment.

a beam pumping unit on which the counterbalancing is done by means of an air cylinder.

an atmospheric fin-tube exchanger that utilizes air for cooling. Ambient air contacts the external fins by fan-forced or natural draft. Also called air-fin unit or aerial cooler.

in a coil of wire carrying electric current, the central interior portion of the coil in which only air exists.

having inadvertent mechanical incorporation of air into a liquid system.

see air-cooled exchanger.

a glass-stem thermometer totally encased in a glass sheath, which provides air space between the thermometer and the liquid in which the unit is immersed.

on an engine, a device powered by compressed air that starts the engine. The compressed air, when allowed to enter the starter motor by means of a valve, causes a gear on the starter to engage a gear attached to the outer edge of the engine’s flywheel. The rotating starter gear moves the flywheel gear, which causes the engine’s pistons to move. If fuel, air, and, on spark-ignition engines, electric spark are present in the engine, the engine will start after a few rotations. As soon as the engine starts, the starter gear disengages from the flywheel gear. Air-motor starters are installed on large industrial engines like those used on a drilling rig.

in a liquid-level control system, a device consisting of a pipe submerged in the liquid whose outlet is connected above the vessel in which the level is to be maintained. It represents a zero reference level.

a method, similar to a diaphragm box, that overcomes objections of internal mounting in corrosive liquids and effects of high temperature. A box is placed in a position to trap air under the box and liquid pressure is transmitted to an indicator-recorder.

a body designed to provide a desired reaction force when in motion relative to the surrounding air.

a warning device triggered by the presence of abnormal conditions in a machine or system. For example, a low-water alarm automatically signals when the water level in a vessel falls below its preset minimum. Offshore, alarms are used to warn personnel of dangerous or unusual conditions, such as fires and escaping gases.

a surveying instrument consisting of sighting device, index, and reading or recording device.

hydrocarbons that have a straight chain of carbon atoms. Compare aromatic hydrocarbons.

see aliphatic hydrocarbons.

a series of open-chained hydrocarbons. The two major classes are the series with saturated bonds and the series with unsaturated bonds.

a substance having marked basic (alkaline) properties, such as a hydroxide of an alkali metal. See base.

having a pH of more than 7; a liquid alkaline solution turns red litmus paper blue.

a method of improved recovery in which alkaline chemicals such as sodium hydroxide are injected during a waterflood or combined with polymer flooding. The chemicals react with the natural acid present in certain crude oils to form surfactants within the reservoir. The surfactants enable the water to move additional quantities of oil from the depleted reservoir. Compare polymer flooding, waterflooding.

the combining power of a base, or alkali, as measured by the number of equivalents of an acid with which it reacts to form a salt. Any solution that has a pH greater than 7 is alkaline. See pH.

see paraffin.

a chemical family of specific organic compounds, including mono­ethan­o­­l­amine (MEA), diethanola­mine (DEA), and tri­ethanolamine (TEA). These chemicals, and proprietary mixtures containing them and other amines, are used extensively for the removal of hydrogen sulfide and carbon dioxide from other gases and are particularly adapted for obtaining the low acid gas residuals that are usually specified by pipelines.

a continuous-operation liquid process for removing acid gas from natural gas by using chemical absorption with subsequent heat addition to strip the acid gas components from the absorbent solution.

a compound derived from an alkane by removing one hydrogen atom.

a process for manufacturing components for 100-octane gasoline. An alkyl group is introduced into an organic compound either with or without a catalyst. Now usually used to mean alkylation of isobutane with propene, butenes, or hexenes in the presence of concentrated sulfuric acid or anhydrous hydrofluoric acid.

in tank sampling, a sample that is obtained by submerging a stoppered beaker or bottle to a point as near as possible to the draw-off level, then opening the sampler and raising it at a rate that makes it about three-quarters full (maximum 85%) as it emerges from the liquid.

a fishing device used to pick up relatively small objects like wrenches that have fallen or have been dropped into the wellbore. The alligator grab’s jaws are pinned open before the tool is run into the well. The jaws snap shut over the fish when contact is made.

a phenomenon that occurs in paint and other coatings, which is characterized by wide and extensive breaks in the paint or coating that do not penetrate to the substrate.

the distribution of oil or gas produced from a well per unit of time. In a state using proration, this figure is established monthly by its conservation agency.

see tail gate.

see rider.

Native American land designated for use by a specific individual, although the title is still held by the United States.

the amount of oil or gas that can be produced legally from a well. In a state using proration, this figure is established monthly by its conservation agency. See proration.

a substance with metallic properties that comprises two or more elements in solid solution. See ferrous alloy, nonferrous alloy.

a large, sloping sedimentary deposit at the mouth of a canyon, laid down by intermittently flowing water, especially in arid climates, and composed of gravel and sand. The deposit tends to be coarse and unworked, with angular, poorly sorted grains in thin, overlapping sheets. A line of fans may eventually coalesce into an apron that grows broader and higher as the slopes above are eroded away.

a metal alloy of aluminum, nickel, and one or more of the elements cobalt, copper, and titanium. This alloy is used to make strong permanent magnets.

a permanent magnet made from the alloy alnico. See alnico.

articulated loading platform.

one of the extremely small particles of an atom that is ejected from a radioactive substance (such as radium or uranium) as it disintegrates. Alpha particles have a positive charge.

current that flows in one direction in a circuit and then reverses flow. Reversal of current flow happens rapidly-for example, in many AC circuits in the United States, reversal happens 60 times in 1 second.

in an alternating current generator, the rising and falling of induced positive and negative voltage as the coil rotates from 0 to 180 degrees to produce positive voltage and from 180 to 360 degrees to produce negative voltage. The rising and falling of positive voltage from 0 to 180 degrees is one alternation. The rising and falling of negative voltage from 180 to 360 degrees is also one alternation. One positive and 1 negative alternation is 1 cycle.

an electric generator that produces alternating current.

a white or gray mid-level cloud that appears as closely arranged rolls. This type of cloud is composed of either ice crystals or water droplets.

a bluish or grayish layer of uniform mid-level clouds that cover large portions of the sky. This type of cloud is composed of either ice crystals or water droplets.

aluminum oxide (Al2O2), used as an abrasive, refractory, catalyst, and adsorbent.

an alloy of copper and aluminum that may also include iron, manganese, nickel, or zinc.

wireline made of braided aluminum wires, which is strengthened by the addition of steel wires, and which conducts electricity.

an aluminum salt of stearic acid used as a defoamer. See stearate.

amplitude modulation.

states that the volume occupied by a mixture of gases equals the sum of the volumes each gas would occupy at the pressure and temperature of the mixture.

the conditions (pressure, temperature, humidity, etc.) of the medium surrounding the case of a meter, instrument, transducer, etc.

the pressure of the medium that surrounds an object.

the temperature of the medium that surrounds an object.

a wireline instrument for measuring bottomhole temperature or pressure. It contains a clock-driven recording section and either a pressure element or a temperature element. It is thin enough to pass downhole through small tubing.

a leading national industry organization established to disseminate scientific and technical ideas and data in the field of geology as it relates to oil and natural gas exploration and production. Its official publications are the AAPG Bulletin and the AAPG Explorer. Address: P.O. Box 979; Tulsa, OK 74101; 918-584-2555.

an international trade organization of landmen and related professionals. Its official publication is The Landman. Address: 4100 Fossil Creek Blvd.; Fort Worth, TX 76137; 817-847-7700.

a leading ship classification society, its main purpose is to determine the structural and mechanical fitness of ships and other marine structures through classification procedures. ABS establishes and administers standards, known as rules, for the design, construction, and operational maintenance of marine vessels and structures. They operate as three divisions: ABS Americas, ABS Europe, and ABS Pacific. Corporate headquarters are in Houston, Texas. Address: ABS Plaza, 16855 North­chase Drive, Houston, TX 77060; 281-877-5800; www.eagle. org.

a professional multinational organization of persons employed by governmental units responsible for full-time programs of hygiene and worker health and protection. Address: 1330 Kemper Meadow Drive; Cincinatti, Ohio 45240; 513-742-2020.

a national trade association whose members are U.S. and Canadian distributors of natural, manufactured, and mixed gases. AGA provides information on sales, finances, utilization, and all phases of gas transmission and distribution. Its official publications are AGA Monthly and Operating Section Proceedings. Address: 400 N. Capitol Street, NW; Washington, DC 20001; 202-824-7000; fax 202-824-7115.

parent group of the Society of Petroleum Engineers (SPE). See Society of Petroleum Engineers. Its official publication is the Journal of Petroleum Technology. Address: P.O. Box 270728, Littleton, CO 80127; 303-948-4255.

serves as clearinghouse for nationally coordinated voluntary standards for fields ranging from information technology to building construction. Address: 25 W. 43rd Street, NY, NY 10036.

an oil trade organization (founded in 1920) that is the leading standardizing organization for oilfield drilling and producing equipment. Headquartered in Washington D.C., it publishes materials concerning exploration and production, petroleum measurement, marine transportation, marketing, pipelining, refining, safety and fire protection, storage tanks, valves, training, health and environment, policy, and economic studies. Address: 1220 L Street NW; Washington, DC 20005; 202-682-8000; www.api.org.

an organization (now called ASTM International) that sets guidelines for the testing and use of equipment and materials. Its publications are ASTM Standardization News, Book of Standards, Cement and Concrete Aggregates Journal, Composites Technology & Research, Geotechnical Testing Journal, Journal of Forensic Science, and Journal of Testing and Evaluation. Address: 100 Barr Harbor Dr.; West Conshohocken, PA 19428-2959; 610-832-9500.

organization whose equipment standards are sometimes used by the oil industry. Its official publication is Mechanical Engineering. Address: 3 Park Avenue; New York, NY 10016; 212-591-7000; fax 212-591-7739.

organization that establishes safety practices for several industries. Its publications are Professional Safety and Society Update. Address: 1800 East Oak­ton; Des Plaines, IL 60018-2187; 847-699-2929.

in computer science, a standard for assigning numerical values to the set of letters in the Roman alphabet and to typographic characters. For example, in ASCII code, the binary number 1001011 is assigned the letter K, and the binary number 1011110 is assigned the typographic character ^.

outdated specification for supplies and equipment purchased by the military in World War II. It has been replaced by military specification (MIL).

a standard that assigns a number (a gauge) to electrical wires of various diameters, or sizes. The largest AWG wire is listed as 0000, which is often written as 4/0, and has a diameter of 460 mils, or 0.46 inches. (A mil is 0.001 inches.) A wire often used in small household appliances, such as small table lamps, is 16 gauge, which is 51 mils, or 0.051 inches, in diameter. The smallest is 40-gauge wire, which is 3.1 mils, or 0.0031 inches in diameter. As the AWG number increases, the gauge (thickness) of the wire decreases.

area of mutual interest.

the half-way point in the overall length of a floating offshore drilling rig, especially a drill ship.

1. any of several compounds employed in treating natural gas. Amines are generally used to remove hydrogen sulfide from water solutions and carbon dioxide from gas or liquid streams. n, adj: 2. an organic compound that contains nitrogen as the key atom and is basic. Amines resemble ammonia in which one or more hydrogen atoms are replaced by organic substitutes such as alkyl and aryl groups.

see organophilic clay.

an organic compound derived from ammonia, in which organic compounds replace one or more of the hydrogen atoms in the ammonia.

a group of processes that use aqueous solutions of various amines to remove hydrogen sulfide (H2S) and carbon dioxide (CO2) from gases. Includes an absorber unit and a regenerator unit as well as accessory equipment.

an instrument for measuring electric current in amperes.

1. the return of a debt (principal and interest) in equal annual installments. 2. the return of invested principal in a sinking fund.

ampere.

the fundamental unit of electrical current; 1 ampere = 6.28 ×  1018 electrons passing through the circuit per second. One ampere delivers 1 coulomb in 1 second.

the number of turns in a coil multiplied by the number of amperes of current flowing through the coil.

a unit of electricity equal to the amount produced in 1 hour by a flow of 1 ampere. See ampere.

a measure of a battery’s ability to produce current in terms of ampere-hours. For example, if a battery has an ampere-hour rating of 30, the battery could produce 1 ampere of current for a 30-hour period.

an electronic device for increasing the magnitude of a quantity such as an electrical measurement signal. Amplifiers may be used to increase a transmitted and received measurement signal.

1. in marine architecture, the maximum absolute value of a periodically varying quantity, such as the roll of a floating vessel. 2. in electronics, a measure of the extent of a vibratory movement, or an oscillation. It expresses the maximum deviation that a periodically varying quantity takes from its normal value of zero. 3. in well logging, the shapes and heights of the peaks in a spontaneous potential curve. 4. a measure of the extent of a vibratory movement, or an oscillation. It expresses the maximum deviation that a periodically varying quantity takes from its normal value of zero.

the varying (modulating) of a wave in which the height (amplitude) of the wave is the characteristic varied in accordance with the intelligence to be transmitted. Compare frequency modulation.

active in the absence of free oxygen.

bacteria that do not require free oxygen to live or that are not destroyed by its absence. Under certain conditions, anaerobic bacteria can cause scale to form in water-handling facilities in oilfields or hydrogen sulfide to be produced from sulfates.

1. of or pertaining to an instrument or equipment that measures a continuous variable that is proportional to another variable over a given range. For example, temperature can be represented or measured as voltage, its analog. 2. pertaining to devices, data, circuits, or systems that operate with variables that are represented by continuously measured voltages or other quantities. Compare digital.

information indicated by a continuous form, usually a needle or pointer moving across a dial face. Compare digital readout.

a device in a programmable logic controller (PLC) that accepts an analog signal from a proportional transmitter and converts the analog signal to a digital signal for processing by the system processor.

a device in a programmable logic controller (PLC) that typically delivers an analog current signal of 4 to 20 milliamps (mA) to an analog transducer such as a current-to-pressure (I/P) transducer.

the representation of the magnitude of a variable in the form of a measurable physical quantity that varies smoothly rather than in discrete steps.

examination and testing of the drilling fluid to determine its physical and chemical properties and condition.

a device that secures, or fastens, equipment. In producing wells with sucker rod pumps, a gas anchor is a special section of perforated pipe installed below the pump. It provides a space for gas to break out of the oil. In offshore drilling, floating drilling vessels are often secured over drill sites by large anchors like those used on ships. For pipelines, a device that secures pipe in a ditch. In deck gratings on offshore installations, the device that secures the grating to its supports is an anchor.

a structure (usually tubular) that is mounted on a vessel’s hull to allow the racking of anchors.

a floating marker used in a spread mooring system to position each anchor of a semisubmersible rig or drill ship. See spread mooring system.

the top part of an anchor fluke to which the anchor pendant (or pennant) is attached.

the part of a drag embedment anchor (DEA) that embeds into the seafloor (either wholly or partially) and provides the greatest amount of anchor-holding capacity.

a device on the deadline tie-down anchor used to secure the drilling line.

a packer designed for sitting on a pipe that rests on bottom, such as a tail pipe or liner. See packer.

the pattern of minute projections from a metal surface produced by sandblasting, shot blasting, or chemical etching to enhance the adhesiveness of surface coatings.

a system of wire, chain, connectors, and buoys connected to the crown of an anchor which is used to buoy off the anchor. It is used in anchor deployment or recovery when a permanent chain chaser (PCC) is not used.

a seal assembly run on the production tubing that allows the tubing to be landed properly in the casing’s seal bore when tubing weight alone is not sufficient to seat the tubing.

the connector used to connect wire, chain, or a swivel to an anchor.

the part of an anchor to which the fluke is connected at the base and to which the mooring wire and/or chain is connected at the top.

a fishing tool installed inside washover pipe to prevent a fish stuck off bottom from falling to bottom during a washover. Slips on the anchor washpipe spear engage the inside of the washover pipe as the pipe travels downhole around the fish.

a weight installed in a tank to which the guide wires or cables for an automatic tank gauge float are attached to hold them taut and plumb.

a combined supply and anchor-handling ship. The AHTS is an offshore supply vessel specially designed to provide anchor-handling services and to tow offshore rigs, platforms, barges, and production modules/vessels. The vessel is often used as a standby rescue vessel for oilfields in production. The AHTS is often equipped for fire fighting, rescue operations, and oil recovery. The AHTS is also used in general supply service for all kinds of platforms, transporting both wet and dry cargo in addition to deck cargo.

a relatively small but powerful watercraft used to set and retrieve anchors that moor an offshore drilling unit on location.

in pipeline construction, a combination of anchors used to hold a lay barge on station and move it forward along the planned route. Lay-barge anchors may weigh in excess of 20 tons (18 tonnes), and a dozen or more may be needed.

a circuit that has two or more input-signal ports that deliver an output only if and when every input port is simultaneously energized.

finely crystalline, generally light-colored extrusive igneous rock composed largely of plagioclase feldspar with smaller amounts of dark-colored minerals. Compare diorite.

1. a suffix used in names of hydrocarbons of the methane propane series. 2. a saturated hydrocarbon. The suffix ane indicates that the hydrocarbons are paraffinic hydrocarbons with the chemical formula CnHn+4. Thus, the paraffinic hydrocarbon pentane, for example, has the formula C5H9; octane has the formula C8H12.

an instrument for measuring wind speed in the atmosphere. The most common types are cup, vane, and hot-wire anemometers.

a barometer consisting of a flexible, spring-filled metal cell from which air has been removed and a mechanism that registers. See barograph.

an accessory which measures the angle of the boom above horizontal.

the difference, in angular degrees, between magnetic north and true north.

in directional drilling, the angle at which a well diverts from vertical; usually expressed in degrees, with vertical being 0°.

see drift angle.

the angle at which a formation dips downward from the horizontal.

see drift angle.

the angle in degrees that a floating vessel inclines to one side or the other.

in crane operations, when a sling with two legs is attached to each end of a load, the slant or the angle the two legs make as measured from horizontal. A reduction in the strength of a sling must be allowed for angles other than 90 degrees.

see heel.

the distance that the brake band wraps around the brake flange. Drawworks have an angle of wrap of 270° or more.

see bent sub.

see riser angle indicator.

the part of a groove on the drawworks drum that changes direction. Grooves run parallel to each other, except in the angle-control section, where each groove is machined at a slight angle. This angled part of the groove causes the wire rope being spooled onto the drum to change direction so that the next wrap of rope on the drum lies in between the wraps of rope already on the drum. Also called a crossover section.

a type of thermometer used on oil tanks. The graduated part of the thermometer is angled at least 90° from the temperature-sensitive portion. The angle conforms to the shell of the tank and permits easy reading of the instrument.

a glass-stem thermometer in which the tail is bent at an angle to the stem so that the tail can be mounted in a horizontally disposed thermowell, leaving the scale vertical for greater ease of reading.

younger sediments that rest upon eroded surfaces of filtered or folded rocks. Subsection of a system that separates younger from older strata.

one type of misalignment in a chain-and-sprocket drive. The shafts are not parallel to each other (they form an angle) in either the horizontal or the vertical plane. This pulls the link plates on one side tighter than those on the other side; thus, one side of the chain and sprockets wears faster than the other. Link plates on only one side of the chain break because of fatigue.

an unconformity in which formations above and below are not parallel. See unconformity.

a measure of the time required for a flowing medium, such as a fluid, to change its angular displacement.

the common name for anhydrous calcium sulfate, CaSO4.

without water.

liquid chemical derived from benzene or from benzene and ammonia. It is used as a solvent and in the organic synthesis of other substances.

the lowest temperature at which the chemical aniline and a solvent (such as the oil in oil-base muds) will mix completely. In general, the oil of oil-base muds should have an aniline point of at least 150°F (66°C) to obtain maximum service life from the rubber components in the mud system.

1. a negatively charged ion. 2. the ion in an electrolyzed solution that migrates to the anode. See ion. Compare cation.

glass that has been treated with a heating and cooling process that toughens it and reduces its brittleness.

the date, usually one year from the effective date of the lease, by which rentals must be paid to maintain the lease in effect in the absence of drilling or production.

a gas measurement device that consists of a multiple-ported Pitot tube installed inside a pipe through which gas is flowing; it is installed perpendicular to the flow of gas. The length of the annubar is equal to the diameter of the pipe in which it is installed. An annubar senses the difference between total flowing pressure and static pressure; gas volume is calculated from this difference. See Pitot tube.

pertaining to the annulus. The annulus is sometimes referred to as the annular space.

a large valve, usually installed above the ram blowout preventers, that, when closed, forms a seal in the annular space between the pipe and the wellbore or, if no pipe is present, in the wellbore itself. Compare ram blowout preventer.

in drilling from floating off­shore drilling rigs using a subsea blowout preventer stack and a Cameron model HC hydraulic connector, which is a device that connects the lower marine riser package (LMRP) to the subsea blowout pre­venter stack, a solid cylinder (a piston) that completely surrounds the locking segments in the connector and which provides an additional locking force. The additional locking force available through the annular piston increases the pressure rating to 15,000 psi (105,000 kPa). See hydraulic connector, lower marine riser package.

fluid pressure in an annular space, as around tubing within casing.

a reduction in the pressure of the fluid in the annulus caused by its motion against the wellbore, which may be open or cased. As the fluid moves through the annulus, friction between the fluid and the annular wall and within the fluid itself creates a pressure loss. The faster the fluid moves, the greater are the losses.

see annular blowout preventer.

production of formation fluids through the production casing annulus.

1. the space that surrounds a cylindrical object within a cylinder. 2. the space around a pipe in a well­bore, the outer wall of which may be the wall of either the borehole or the casing; sometimes termed the annulus.

a valve installed on the surface of a well which, when closed, seals the annular space between the tubing and the casing.

the rate at which mud is traveling in the annular space of a drilling well.

see annular space.

a valve on a wellhead that, when closed, isolates the annulus if well fluids enter the annulus because a packer or the tubing fails. The valve is normally closed during production operations unless the well is on gas lift, in which case, it is opened.

see production swab valve.

if gas lift is required, it is used to control the fluid flow from the gas-lift line into the annulus.

a signaling device that operates electromechanically and serves to indicate visually or visually and audibly whether current is flowing, has flowed, or has changed direction of flow in one or more circuits.

1. one of two electrodes in an electrolytic cell; represented as the negative terminal of the cell, it is the area from which electrons flow. In a primary cell, it is the electrode that is wasted or eaten away. 2. in cathodic protection systems, an electrode to which a positive potential of electricity is applied, or a sacrificial anode, which protects a structure by forming one electrode of an electric cell. 3. in a semiconductor diode, the terminal toward which forward current flows from an external circuit. See diode.

a deviation from the norm. In geology the term indicates an abnormality such as a fault or dome in a sedimentary bed. Plural form: anomalies.

an undersupply of oxygen reaching the tissues of the body, possibly causing permanent damage or death. Also called hypoxia.

American National Standards Institute.

in meteorology, an area that separates cold air from the Antarctic from the warm air that lies north of the South Pole. Sometimes called a polar front.

a hydrate inhibitor that limits the size of hydrate crystal formation to a fraction of a millimetre.

1. in designing or ordering hoisting (lifting) equipment, the maximum weight that the equipment will be able to safely lift. 2. on diesel electric rigs, the maximum amount of electric power that the generators will have to produce to adequately power the rig.

pressure expected to be measured at the surface after a well is drilled and completed.

a hydrocarbon trap in which petroleum accumulates in the top of an anticline. See anticline.

rock layers folded in the shape of an arch. Anticlines sometimes trap oil and gas. Compare syncline.

a large system of atmospheric high pressure marked by circulating winds moving clockwise from the center in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Compare cyclone.

the wind associated with a high-pressure area.

a chemical added to the drilling fluid to minimize the possibility of the drill stem becoming stuck to the side of the hole.

in a ram blowout preventer, a flat steel piece (a plate) on the ram block that prevents rubber from being forced out of the area between the drill pipe and the ram block when wellbore pressure is applied, and which feeds reserve rubber into contact with the drill pipe as rubber is lost because of wear. See ram, ram blowout preventer.

a substance used to prevent foam by greatly increasing surface tension. Compare defoamer.

a chemical added to liquid that lowers its freezing point. Often used to prevent water in an engine’s cooling system from freezing.

a substance, such as tetraethyl lead or other compounds, added to the fuel of an internal-combustion engine to prevent detonation of the fuel. Antiknock compounds effectively raise the octane rating of a fuel so that it burns properly in the combustion chamber of an engine. See octane rating, tetraethyl lead.

the measurement of how well an automotive gasoline resists detonation or pinging in a spark-ignition engine.

antilogarithm.

a second number whose logarithm is the first number. See logarithm.

common additives which prevent an acid from reacting with certain types of crude and forming an insoluble sludge that blocks channels or reduces permeability.

a drill bit, usually a polycrystalline diamond bit, that is designed to prevent the bit’s drilling a spiral-shaped hole because it whirls off-center as it rotates. See bit whirl.

Arctic National Wildlife Refuge.

absolute open flow.

absolute open flow potential.

cross-sectional area through the packer seal, in2.

American Petroleum Institute.

a classification system for oilwell cements, defined in API Specification 10A.

the standard unit of gamma ray measurement. Standardization of this unit results from the normalization of the detector-measurement systems of all primary service companies in the API test pits at the University of Houston. The API gamma ray unit is defined as 1/200  of the difference in log deflection between two zones of different gamma ray intensity. The test pit is constructed so that the average midcontinent shale will record about 100 API gamma ray units.

the measure of the density or gravity of liquid petroleum products on the North American continent, derived from relative density in accordance with the following equation: API gravity at 60°F = 141.5/specific density – 131.5. API gravity is expressed in degrees, a specific gravity of 1.0 being equivalent to 10° API. See gravity.

American Petroleum Institute’s Manual of Petroleum Measurement Standards.

the standard unit of measurement for neutron logs. Standardization of this unit results from the calibration of each logging tool model in the API neutron test pit at the University of Houston.

a scale of liquid gravity measurement units called degrees API, devised and adopted by the American Petroleum Institute. Although the scale is very different from an ordinary specific gravity scale, it bears a definite relation to it as follows: 140 °API = G – 130 where G is specific gravity of the petro­leum with reference to water, both at 60°F. The API scale has particular advantages: it provides finer graduations between whole number units and lends itself to schemes for correcting to a temperature standard of 60°F.

API Specification for Rotary Drilling Equipment, a publication that lists the specifications for drilling equipment.

publications developed and written by knowledgeable and experienced persons-often employees of oil companies that are API members-to establish standard manufacturing, handling, inspection, and other aspects of oilfield equipment, materials, and practices. API standards cover such sectors of the petroleum and natural gas industry as drilling, producing, pipelining, refining, and measuring. Once the documents are written, API publishes and distributes them to the oil industry and other interested parties. An example of a standard is API Specification 6A, Wellhead and Christmas Tree Equipment, which provides manufacturing specifications for equipment used in pressure control systems for the production of oil and gas. API also publishes recommended practices (RPs) and documents such as technical reports, bulletins, and forms. RPs give recommended practices that personnel should follow when performing certain operations. For example, RP 13A, Standard Procedure for Field Testing of Water-Based Drilling Fluids, shows the equipment procedures that personnel should use to test water-based drilling fluids in the field. Bulletins provide information and guidance about practices that affect the petroleum industry. For example, Bulletin D10, Procedure for Selecting Rotary Drilling Equipment, describes a system of analysis to select a rig suitable for drilling a specific well. Technical reports cover a variety of subjects, such as the results of API-sponsored research. API also publishes special items such as forms and additional documents that do not fall under the previous categories. For example, Form 5UO1, Voluntary Unit Agreement, provides a common standard of reference for parties involved in forming a cooperative operation to increase the ultimate recovery of oil and gas. Publication 4633, Barium in Produced Water: Fate and Effects in the Marine Environment, summarizes information about the physical and chemical behavior of barium in the ocean. For further information, contact API at www.api.org or call 202-682-8000.

after payout; commonly used in the land department of an oil company.

the algebraic sum of the actual compressibility of a liquid and the volume change per unit volume of the confining container caused by a unit change in pressure at constant temperature.

the vector sum of the power in watts plus the reactive power in volt-ampere reactive (var) in a circuit. See reactive power.

the viscosity of a drilling fluid as measured with a direct-indicating, or rotational, viscometer.

a well drilled to confirm and evaluate the presence of hydrocarbons in a reservoir that have been found by a wildcat well.

a trademark name for an annular pressure-responsive valve for a DST string.

1. a body of coarse, poorly sorted sediments formed by the coalescence of alluvial or detrital fans along the flanks of a mountain range. 2. a similar body of turbidite sediments formed by the coalescence of submarine debris fans along the base of the continental slope.

the graphite coating on the inside of certain cathode-ray tubes. It collects secondary electrons emitted by the face of the tube.

water or related to water.

1. a permeable body of rock capable of yielding groundwater to wells and springs. 2. the part of a water drive reservoir that contains the water.

a section of a circle, an ellipse, or other curved figure.

a special type of circuit breaker that has a coil and special electronic circuitry that can sense the small fault currents created by arcing between components and that trips the circuit to prevent fires caused by arcing.

to join metals by utilizing the arc created between the welding rod, which serves as an electrode, and a metal object. The arc is a discharge of electric current across an air gap. The high temperature generated by the arc melts both the electrode and the metal, which fuse.

the formula for evaluating the quantity of hydrocarbons in a formation. The form of the equation depends on its specific use. The basic equation is Sw2 = aRw /0mRt.

the buoyant force exerted on a body suspended in a fluid is proportional to the density of the fluid.

in meteorology, an area that separates cold air from the Arctic from warm air that lies south of the North Pole. Sometimes called a polar front.

nineteen million acres on Alaska’s northeast coast that are believed to contain 600 million to 9 billion barrels (954 billion to 143 trillion litres) of oil. Opening of the area to oil exploration and production is the subject of much debate between environmentalists and oil-industry personnel.

a mobile submersible drilling structure used in arctic areas. The rig is towed onto the drilling site and submerged during periods when the water is free of ice. All equipment below the waterline is surrounded by a caisson to protect it from damage by moving ice. The drilling deck has no square corners so that moving ice can better flow around it. See submersible drilling rig.

the extent of a surface enclosed within a boundary; the extent of the surface of all or part of a solid. For two-dimensional plane surfaces, area is usually stated in square units. For example, a rectangle 2 feet long on one side and 3 feet long on the other side has an area of 2 ×  3 feet, which equals 6 square feet (ft2). Thus, the area of the rectangle is 6 ft2.

an employee of a drilling contractor whose job is to coordinate and oversee the contractor’s drilling projects in a particular region or area.

an area, usually outlined on a plat attached to a farmout agreement or described in an exhibit, that allows both parties the first right of refusal on leases acquired by either party after the agreement is executed.

pertaining to sand or sandy rocks (such as arenaceous shale).

a sandstone in which less than 15% of the total volume is silt and clay.

pertaining to a formation that consists of clay or shale (such as argillaceous sand).

in a computer, a circuit or component that changes (converts) electronic signals into units that additional circuitry can add, subtract, multiply, divide, or compare.

sandstone composed largely of feldspar grains and deriving from granitic source rocks.

negotiations between a willing buyer and a willing seller, which should result in a price that truly reflects the market.

a part made of coils of wire placed around a metal core, in which electric current is induced in a generator, or in which input current interacts with a magnetic field to produce torque in a motor.

a corrosion-resistant metal case in which a glass-stem thermometer can be placed to minimize the risk of breakage.

hydrocarbons derived from or containing a benzene ring. Many have an odor. Single-ring aromatic hydrocarbons are the benzene series (benzene, ethylbenzenes, and toluene). Aromatic hydrocarbons also include naph­tha­lene and anthracene. Compare aliphatic hydrocarbons.

see aromatic hydrocarbons.

see aromatic hydrocarbons.

the conversion of aliphatic or alicyclic compounds to aromatic hydrocarbons.

a French unit of measurement, equal to 191.833 feet (58.5 metres).

a chemical element that occurs as a brittle, steel-gray hexagonal mineral and that is added as an impurity to semiconductors to give them a negative charge.

in wells, especially water wells, a phenomenon in which the water produced by the well flows to the surface without the necessity of a lifting (pumping) system. An artesian well is a well drilled through impermeable rock layers into a rock layer that is charged with water from an area at a higher altitude than that of the well, so pressure forces the water to flow upwards.

a well in which water flows to the surface under natural pressure.

off­shore platform in which the riser is jointed to allow for changes in water level, current, and so on.

an artificial gravel island sometimes used in shallow Arctic waters as a base on which drilling and production equipment is erected.

any method used to raise oil to the surface through a well after reservoir pressure has declined to the point at which the well no longer produces by means of natural energy. Sucker rod pumps, gas lift, hydraulic pumps, and submersible electric pumps are the most common means of artificial lift.

a bar or other shape of soft iron or hard steel alloy that is magnetized by placing the bar or other shape in a magnetic field. Magnetite (lodestone) is a natural magnet; other magnets are thus artificial.

an information-collecting instrument that orbits the earth.

altostratus.

arsenic.

the number of Btus contained in a cubic foot of natural gas adjusted to reflect the actual water content of the gas at delivered pressure, temperature, and gravity conditions.

term applied to many heat resistant and chemically inert fibrous minerals, some forms of which are used in certain drilling fluids. It finds only limited use because prolonged exposure can cause respiratory illness.

a wrapping material consisting of asbestos saturated with asphalt; one element of pipeline coatings. It is no longer commonly used because asbestos can cause respiratory illness.

American standard code for information interchange.

noncombustible residue from the gasification or burning of coal or a heavy hydrocarbon.

American Society of Mechanical Engineers.

the ratio of a screen’s (or frame’s) width to the screen’s height. For television sets in the U.S. and Great Britain, for example, the TV screen’s aspect ratio is 3 to 4, which means that if the screen’s height is 3 inches, its width is 4 inches; or, if its height is 12 inches, its width is 16 inches.

a hard brown or black material composed principally of hydrocarbons. It is insoluble in water but soluble in gasoline and can be obtained by heating some petroleums, coal tar, or lignite tar. It is used for paving and roofing and in paints.

an asphalt-base enamel applied as a coating to pipe that is to be buried. The asphalt is combined with finely ground mica, clay, soapstone, or talc and applied while hot. Combined with a subsequent wrapping, this coating protects the buried pipe from corrosion.

an vessel that holds liquid asphalt, a derivative of the crude oil refining process and one of the heaviest and most viscous parts of the petroleum. 

see naphthene-base oil.

petroleum with a high proportion of naphthenic compounds, which leave relatively high proportions of asphaltic residue when refined.

one of a group of solid, liquid, or semisolid materials that are predominantly mixtures of heavy hydrocarbons and their nonmetallic derivatives and are obtained either from natural bituminous deposits or from the residues of petroleum refining.

in internal combustion engines, the method which the engine uses to take air into its cylinders. Engines can be naturally aspirated, which means that the pistons draw in air at atmospheric pressure as they move down the cylinder; or they can be blown or supercharged, in which an engine-driven compressor of some type raises the pressure of the air above that of the atmosphere and forces it into the cylinder.

the analysis of a substance, such as an ore, to determine its components.

American Society of Safety Engineers.

a group of components that make up a mechanism, machine, or similar device.

a transfer of rights and interests in real or personal property or rights under a contract-for example, the transfer of an oil and gas lease from the original lessee to another party.

a clause in any instrument that allows either party to the instrument to assign all or part of his or her interest to others.

a member of a drilling rig’s crew whose job is to aid and assist the driller during rig operations. This person not only controls the drilling operation at certain times, but also keeps records, handles technical details, and, in general, keeps track of all phases of the operation. See driller.

an employee of a drilling contractor whose job includes aiding the rig superintendent; in some cases, the assistant rig superintendent takes over for the rig superintendent during nighttime hours. Consequently, the assistant rig superintendent is sometimes called the night toolpusher. See rig superintendent.

see associated gas.

natural gas that overlies and contacts crude oil in a reservoir. Where reservoir conditions are such that the production of associated gas does not substantially affect the recovery of crude oil in the reservoir, such gas may also be reclassified as nonassociated gas by a regulatory agency. Also called associated free gas. See gas cap. Compare nonassociated gas.

A railroad standards setting organization headquartered in Washington, D.C. AAR members include Amtrak as well as the major freight railroads in the United States, Canada, and Mexico. AAR also works with elected officials in Washington, D.C. Address: 425 Third Street, SW, Suite 1000, Washington, DC 20024; 202-639-2100; www.aar.org.

see Desk and Derrick Clubs.

organization that sets some of the standards, principles, and policies of oilwell servicing contractors. Its official publication is Well Servicing. Address: 14531 FM 529, Suite 250 Houston, TX 770950.; 713-781-0758.

1. at or toward the stern of a ship or an offshore drilling rig; abaft. 2. behind the ship or rig.

American Society for Testing and Materials. Also ASTM International.

any distillation made in accordance with ASTM procedure. Generally refers to a distillation test to determine the initial boiling point, the temperature at which percentage fractionations of the sample are distilled, the final boiling point, and quantity of residue.

Formerly known as the American Society for Testing and Materials, the organization changed its name to ASTM International in 2001. It sets guidelines for the testing and use of equipment and standards throughout the world. Main publication is the bimonthly magazine, “Standardization News.” Address: 100 Bar Harbor Dr., West Conshohocken, PA 19428-2959; Phone: 610-832-9500 Fax: 610-832-9555; www.astm.org.

a sensor located above the bit that communicates real-time inclination measurements while drilling, enabling prompt decisions regarding corrections and changes to the drilling parameters.

from side to side of a ship or offshore drilling rig.

atmosphere.

a unit of pressure equal to the atmospheric pressure at sea level, 14.7 pounds per square inch (101.325 kilo­pas­cals).

total pressure at a depth underwater, expressed as multiples of normal atmospheric pressure.

a one-person atmospheric suit rated to depths of 2,300 feet (701 metres). Advantages include allowing the operator to work in a safe environment for debris salvage or recovery operations.

the pressure exerted by the weight of the atmosphere. At sea level, the pressure is approximately 14.7 pounds per square inch (101.325 kilo­pas­cals), often referred to as 1 atmosphere. Also called barometric pressure.

the aging of specimens for test purposes at normal atmospheric pressure for a designated period of time under specified conditions of temperature and humidity.

a coral island consisting of a reef surrounding a lagoon.

the smallest quantity of an element capable of either entering into a chemical combination or existing alone.

the length of a straight line passing through the center of an atom from one side to the other (the diameter). The approximate diameter of an atom is 10-8 centimetres.

a number that expresses the number of protons and an equal number of electrons in each atom of an element.

one of the small bits of matter that makes up an atom, such as an electron, proton, or neutron.

a number that approximates the number of protons plus the number of neutrons in an atom; it expresses the relative weights of atoms.

to spray a liquid through a restricted opening, causing it to break into tiny droplets and mix thoroughly with the surrounding air.

an alternate designation for front-end equipment; also, any device that may be added as a unit or assembly.

in crane operations, the relative strength of a sling’s end attachment, such as a loop eye or a swaged terminal, which attaches the sling to the load to be lifted by the crane. The less efficient the attachment is, the more the sling’s strength is reduced.

smaller-sized hoses used to put out small fires or a fire that is more or less under control.

a fibrous clay mineral that is a viscosity-building substance; used principally in saltwater-base drilling muds. Also called fuller’s earth.

in electronics, a small device (a probe) that is put into contact with or inserted into a circuit to make measurements of the circuit and that reduces (attenuates) the strength of the value (such as voltage) being measured in the circuit. The amount of attenuation is usually expressed as a ratio-for example, a 10-to-1 probe reduces the values strength by 10.

to verify or witness, by a designated company official, the signature of the signing company officer and the affixing of the official company or corporation seal. The title of the company official executing the instrument and the title of the company official attesting it should appear under the signatures.

an iron-core transformer used to bring together (to electronically couple) circuits that carry audio frequencies.

a quantity to which another quantity is added.

a boring tool that consists of a shaft with spiral channels. An auger may be used to bore the hole for a pipeline that must cross beneath a roadbed.

an estimate of costs prepared by a lease operator and sent to each nonoperator with a working interest for approval before work is undertaken. Normally used in connection with well-drilling operations.

see automatic driller.

a plant that contains instruments for the measurement and control of temperatures, pressures, flow rates, and properties of resulting products and thereby makes necessary corrections in the plant operating conditions so as to maintain specification products. Such a plant contains shutdown and other automatic devices for minimizing damage in the absence of operating personnel.

a device that performs some of the actions of a floorhand (a roughneck) on a drilling rig. In general, automated roughnecks pick up stands of drill pipe set back in the derrick and make them up. They also break out stands of drill pipe and set them back in the derrick. Normally, drillers actuate the controls on the automated roughneck from their position on the rig floor.

see breakout cathead, cathead, makeup cathead.

an adjustable choke that is power-operated to control pressure of flow. See adjustable choke.

a device that regulates various factors (such as flow rate, pressure, or temperature) of a system without supervision or operation by personnel. See instrumentation.

a system for automatically measuring and sampling oil or products at points of receipt or delivery. See lease automatic custody transfer.