Glossary

gram.

center of gravity; this abbreviation is used mostly in buoyancy, stability, and trim calculations for offshore drillng rigs.

gig ohm, or 1 billion (1,000,000,000) ohms.

general and administrative expense.

gas- and oil-cut mud; used in drilling reports.

gallium.

generally accepted accounting principles.

an intrusive igneous rock with the same composition as basalt.

variation of gauge.

gallon.

gallons per minute. Also abbreviated as gpm.

a wind that is blowing at 28 to 55 knots. Gales are classified as moderate, fresh, strong, or whole.

lead sulfide. Technical grades (specific gravity about 7) are used for increasing the density of drilling fluids to points impractical or impossible with barite.

damage to steel surfaces caused by friction and improper lubrication.

the result of the sticking or adhesion of two mating surfaces of metal, not protected by a film of lubricant, and tearing due to lateral displacement.

one of the limitations on chain-and-sprocket life. This limitation on the strength of the metal the chains and sprockets are made of may cause the metal to wear even though it is lubricated because of a heavy load or a high speed.

a silvery-white metallic element often added as an impurity to semiconductors to create a positive charge in the semiconductor.

a unit of measure of liquid capacity that equals 3.785 litres and has a volume of 231 cubic inches (0.00379 cubic metres). A gallon of water weighs 8.34 pounds (3.8 kilograms) at 60°F (16°C). The imperial gallon, formerly used in Great Britain, equals approximately 1.2 U.S. gallons.

the amount of liquid a fire-fighting device delivers in U.S. gallons.

an expression of oil-to-gas ratio of the amount of lean oil circulated per million cubic feet of gas through the absorber.

of, relating to, or producing a direct current of electricity.

the production of current flow when two dissimilar metals are placed in an electrolyte.

in cathodic protection, a sacri­ficial anode that produces current flow through galvanic action. See sacrificial anode.

an electrical device that contains two dissimilar metals suspended in or surrounded by an electrolyte, which is capable of producing voltage and current. Two or more galvanic cells constitute a battery. Often, and erroneously, a galvanic cell is called a battery. A battery consists of two or more galvanic cells.

a type of corrosion that occurs when a small electric current flows from one piece of metal equipment to another. It is particularly prevalent when two dissimilar metals are present in an environment in which electricity can flow (as two dissimilar joints of tubing in an oil or gas well).

corrosion prevention employed at the point where dissimilar metals come into contact and at which point corrosion could occur because of the small current created when dissimilar metals touch. The protection interrupts the current flow and thus prevents corrosion. See galvanic cell, galvanic corrosion.

to immerse an iron or steel object in molten zinc to produce a coating of zinc-iron alloy on the object. This zinc-iron coating resists corrosion.

zinc coating for corrosion resistance used to extend the life of wire rope.

steel that is coated with zinc to protect it from rusting.

an instrument that detects or measures a small electric current by movements of a magnetic needle or of a coil in a magnetic field. It can be adapted with shunts or resistors to measure larger currents or voltage. See resistor, shunt.

a short, highly penetrating X-ray emitted by radioactive substances during their spontaneous disintegration. The measurement of gamma particles (sometimes called gamma rays) is the basis for a number of radioactivity well logging methods.

see gamma particle.

a plot of gamma radiation detected in a wellbore.

a device that is capable of sensing and measuring the number of gamma particles emitted by certain radioactive substances.

a type of radioactivity well log that records natural radioactivity around the wellbore. Shales generally produce higher levels of gamma radiation and can be detected and studied with the gamma ray tool. In holes where salty drilling fluids are used, electric logging tools are less effective than gamma ray tools. See radioactivity well logging.

a special gamma ray log that reveals the relative amounts of radioactive uranium, thorium, and potassium in a formation. This information can help identify shales and clays.

trade name for a density log.

the supervisor of a roustabout crew or the person in charge of a pipeline crew.

a platform made to carry a traveling crane and supported by towers or side frames running on parallel tracks.

a short rod on the lower end of the traveling valve of a rod pump. It is attached to the standing valve and is used to pull the valve out of its seat when repairs are needed.

a compressible fluid that completely fills any container in which it is con­fined. Technically, a gas will not condense when it is compressed and cooled, because a gas can exist only above the critical temperature for its particular composition. Below the critical temperature, this form of matter is known as a vapor, because liquid can exist and condensation can occur. Sometimes the terms “gas” and “vapor” are used interchangeably. The latter, however, should be used for those streams in which condensation can occur and that originate from, or are in equilibrium with, a liquid phase.

a tubular, perforated device attached to the bottom of a sucker-rod pump that helps to prevent gas lock. The device works on the principle that gas, being lighter than oil, rises. As well fluids enter the anchor, gas breaks out of the fluid and exits from the anchor through perforations near the top. Remaining fluids enter the pump through a mosquito bill (a tube within the anchor), which has an opening near the bottom. In this way, all or most of the gas escapes before the fluids enter the pump.

comparison of the sum of the volumes of gas production or receipts with the sum of the volumes of the dispositions of the gas.

an agreement between partners in a joint-interest well to determine the share due each partner if the gas is sold to two or more markets. Stated another way, an agreement covering the manner in which volumes of deferred gas production or exchange gas will be balanced between the parties to the agreement.

an excess supply of natural gas, as when the available supply of natural gas exceeds the demand.

see mud-gas separator.

a free-gas phase overlying an oil zone and occurring within the same producing formation as the oil. See associated gas, reservoir.

a machine that removes heat from a liquid through a vapor-compression or absorption refrigeration cycle.

a device used to separate and identify gas compounds by their adhesion to different layers of a filtering medium such as clay or paper, sometimes indicated by color changes in the medium.

a device in which cores are thawed and samples of water and gas in the cores are collected. Neon is added to the system to ensure that a full charge of gas is obtained.

a constant number, mathematically the product of the total volume and the total pressure divided by the absolute temperature for 1 mole of any ideal gas mixture of ideal gases at any temperature.

a mutually negotiated set of rules governing conduct between the parties thereto relating to all matters of common interest.

a process in which gas becomes entrained in a liquid.

a device used to detect and measure any gas in the drilling mud as it is circulated to the surface.

the entity that is responsible for moving natural gas from the pipeline to the consumer. Usually called the local gas company.

a method of diving that avoids the problem of nitrogen narcosis by substituting helium for nitrogen. Often called mixed-gas diving.

a method of drilling that uses natural gas as the drilling fluid. See air drilling.

1. the use of the energy that arises from the expansion of compressed gas in a reservoir to move crude oil to a wellbore. Also called depletion drive. See dissolved-gas drive, gas-cap drive, reservoir drive mechanism. 2. gas drives are also used as a form of secondary recovery in which gas is injected into wells to sweep remaining oil to a producing well.

see air eliminator.

a condition caused by expanding gases which have been taken into and retained in the lungs while breathing under pressure, being forced into the bloodstream or other tissues during ascent or decompression.

when oil and gas are found in the same reservoir under pressure, the drilling of a well into the reservoir releases the pressure, causing the gas to expand. The expanding gas drives the oil toward and up the wellbore. The expansive energy of the gas can be harnessed whether the gas is in solution or forming a cap above the oil.

a district or area from which natural gas is produced.

in well control, the streaming (the flow) of gas from the well when a formation containing gas is penetrated and is not contained by the drilling mud or well-control equipment.

see flow recorder clock.

a discrepancy between a transporter’s receipts and deliveries of natural gas for a shipper. Most pipelines require that shipper’s deliveries to the pipeline and receipts from the pipeline remain essentially in balance within certain tolerances, or the pipeline may assess charges or penalties until the imbalance is rectified.

the injection of gas into a reservoir to maintain formation pressure by gas drive and to reduce the rate of decline of the original reservoir drive. One type of gas injection uses gas that does not mix (i.e., that is not miscible) with the oil. Examples of these gases include natural gas, nitrogen, and flue gas. Another type uses gas that does mix (i.e., that is miscible) with the oil. The gas may be naturally miscible or become miscible under high pressure. Examples of miscible gases include propane, methane enriched with other light hydrocarbons, methane under high pressure, and carbon dioxide under pressure. Frequently, water is also injected in alternating steps with the gas.

see gas input well.

a well into which gas is injected for the purpose of maintaining or supplementing pressure in an oil reservoir. More commonly called a gas injection well.

gas that is purchased, taken on exchange, or injected from storage.

laws such as Charles’s, Boyle’s, and Avogadro’s that describe the behavior of gas volumes under pressure and temperature.

device used to detect combustible hydrocarbons.

the process of raising or lifting fluid from a well by injecting gas down the well through tubing or through the tubing-casing annulus. Injected gas aerates the fluid to make it exert less pressure than the formation does; the resulting higher formation pressure forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas-lift equipment.

see liquefied petroleum gas.

1. a condition sometimes encountered in a pumping well when dissolved gas, released from solution during the upstroke of the plunger, appears as free gas between the valves. If the gas pressure is sufficient, the standing valve is locked shut, and no fluid enters the tubing. 2. a device fitted to the gauging hatch on a pressure tank that enables manual dipping and sampling without loss of vapor. 3. a condition that can occur when gas-cut mud is circulated by the mud pump. The gas breaks out of the mud, expands, and works against the operation of the piston and valves.

the gas meter is probably most evident to consumers of natural gas who use it to monitor their gas usage and form the basis for monthly gas bills. It is an accurate instrument that measures volumetric quantities over a wide range of flow values and does not require any electrical power to operate. Where the gas pressure is not unreasonably low this meter is quite adequate to perform its function.

the process of measuring the amount of gas.

a refined fraction of crude oil somewhat heavier than kerosene and often used as diesel fuel.

the transport of gas molecules through a thin polymeric film from a region of high pressure to one of low pressure. Gas permeation is based on the principle that some gases are more soluble in polymeric membranes and pass more readily through them than other gases.

a transmission system for natural gas or other gaseous material. The total system comprises pipes and compressors needed to maintain the flowing pressure of the system.

liquids recovered from natural gas in a gas processing plant and, in some situations, from field facilities. See natural gas liquids.

the separation of constituents from natural gas for the purpose of making salable products and also for treating the residue gas to meet required specifications.

an agreement under which gas not sold under a percentage of proceeds contract belongs to the producer as it passes through the processing plant. Normal payment is a percentage of the products recovered; the seller retains title to the residue gas.

see natural gas processing plant.

an organization of companies that engages in gas processing. Its official publication is Proceedings. Address: 6526 E. 60th St.; Tulsa, OK 74145; 918-493-3872.

an outgrowth of the Gas Processors Association that is engaged in meeting the supply and service needs of the natural gas and gas processing industry. http://gpsa.gasprocessors.com.

a body of flowing fluid gas.

a manifold of bottle racks containing from 4 to 64 bottles used to provide breathing gases to divers. The bottles are high pressure, up to 50,000 cubic feet (1,416 cubic metres) at 2,800 psi, and are grouped together to create a large volume of available gas. The gas racks can contain breathing air for a secondary source of air in the event the compressor fails. They also contain oxygen for surface decompression or metabolic use during saturation diving, and are used for mixed-gas diving operations.

see regeneration gas.

an automatically operated valve that, by opening and closing in response to pressure, permits more or less gas to flow through a pipeline and thus controls the pressure.

a geological formation containing a single gaseous phase. When produced, the surface equipment may or may not contain condensed liquid, depending on the temperature, pressure, and composition of the single reservoir phase.

a stratum of sand or porous sandstone from which natural gas is obtained.

the amount of gas contained within the porosity of a reservoir.

equipment used to remove any water, hydrocarbons, treating chemicals, or corrosion inhibitors from entering the contactor.

the escape of natural gas to the surface from a formation that contains natural gas. See seep.

see separator.

the gas that appears in drilling fluid returns, indicating the presence of a gas zone.

see explosimeter.

the split-vapor process that uses a fraction of the vapor from the cold separator as the top reflux to the demethanizer after substantial condensation and sub-cooling.

a container connected to the low-pressure side of a refrigerating system that increases gas volume and reduces rate of pressure change. Also called a surge tank.

the central or trunk pipeline system by means of which dry natural gas is transported from field gathering stations or processing plants to the industrial or domestic fuel market. Well pressure is supplemented at intervals along the transmission line by compressors to maintain a flow strong enough to move the gas to its destination.

the removal of hydrogen sulfide and carbon dioxide from raw gas or the green gas stream.

equipment for the processing of natural gas.

an engine in which gas, ­under pressure or formed by combustion, is directed against a series of turbine blades. The energy in the expanding gas is converted into rotary motion.

a well that primarily produces gas. Legal definitions vary among the states.

in the formation of hydrocarbons below the earth’s surface, the range of temperatures and depths at which natural gas is generated and expelled from source rocks. The gas window temperatures range from 100 to 200 degrees C (212 to 392 degrees F) at depths from 3 to 6 km (2 to 4 m). Compare oil window.

an area in a reservoir that is occupied by natural gas.

drive energy supplied naturally (as a reservoir is produced) by the expansion of the gas cap. In such a drive, the gas cap expands to force oil into the well and to the surface. See reservoir drive mechanism.

see associated gas.

see gas-cap drive, reservoir.

a device used in a glycol dehydration system installed where water is being removed from gas condensate; the separator removes glycol from the gas condensate.

a drilling mud that contains entrained formation gas, giving the mud a characteristically fluffy texture. When entrained gas is not released before the fluid returns to the well, the weight or density of the fluid column is reduced. Because a large amount of gas in mud lowers its density, gas-cut mud must be treated to reduce the chance of a blowout.

tools and equipment used in gas-lift wells. The devices include gas-lift valves and gas-lift mandrels. See gas lift, gas-lift mandrel, and gas-lift valve.

a device installed in the tubing string of a gas-lift well onto which or into which a gas-lift valve is fitted. There are two common types of mandrel. In the conventional gas-lift mandrel, the gas-lift valve is installed as the tubing is placed in the well. Thus, to replace or repair the valve, the tubing string must be pulled. In the side-pocket mandrel, however, the valve is installed and removed by wireline while the mandrel is still in the well, eliminating the need to pull the tubing to repair or replace the valve.

a device installed on a gas-lift mandrel, which in turn is put on the tubing string of a gas-lift well. Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing to cause the fluid to rise to the surface. See gas-lift mandrel.

a well in which reservoir fluids are artificially lifted by the injection of gas.

capable of being mixed with gas. See miscible.

see gas injection.

the point or plane in a reservoir at which the bottom of a gas sand is in contact with the top of an oil sand.

a measure of the volume of gas produced with oil, expressed in cubic feet per barrel or cubic metres per tonne. Also called solution gas-oil ratio.

a method that involves an arc struck between a nonconsumable tungsten electrode and the work piece. Filler metal is provided to the weld by a bare metal rod fed into the molten pool by the diver-welder. Commonly referred to as tungsten inert gas welding.

a vertical shell and tube heat exchanger with the feed gas entering the tube channel.

see gas/gas exchanger.

an oilfield term for aerated drilling mud. See aerated drilling mud.

a liquid drilling fluid used in underbalanced drilling into which air or gas is added from the surface.

gas cleaning.

a form of underbalanced drilling in which air or gas is injected into the drill stem from the surface to lower the hydrostatic pressure of a liquid drilling fluid.

a condition in a producing oilwell that occurs when lighter hydrocarbons come out of the oil and reach the surface in gaseous form.

any material (such as paper, cork, asbestos, or rubber) used to seal two essentially stationary surfaces.

a volatile, flammable liquid hydrocarbon refined from crude oils and used universally as a fuel for internal-combustion, spark-ignition engines.

on a diesel engine, a relatively small engine that runs on spark plugs and gasoline and whose power is used to turn over (move) the pistons in the diesel. As the diesel’s pistons move, pressure and heat build in the diesel’s cylinders and the diesel starts. As the diesel begins running, the gasoline engine disengages from the diesel.

also called a natural gas processing plant, a term that is preferred, because it distinguishes the plant from a unit that makes gasoline within an oil refinery. See natural gas processing plant.

a well that produces natural gas.

1. in a logging tool, a shutterlike device that opens and closes very quickly to permit a measurement of the time a formation is exposed to sound, radioactivity, or other energy; usually timed in millionths of a second (microseconds). 2. in solid-state electronics, one of the electrodes in a field-effect transistor. See field-effect transistor.

an opening and closing device (a valve) that employs a slab of metal (a gate) with a hole in it that is moved up or down within the valve’s body. When the hole in the gate is positioned opposite the opening in the valve, fluid flows through the valve. When the solid part of the gate is positioned opposite the valve’s opening, flow stops. Gate valves are not used to regulate the flow of fluids through them—that is, they are either fully open or fully closed.

in an AC-DC diesel-electric system, the small amount of electricity applied to a silicon-controlled rectifier (SCR) to cause electricity to flow in one direction through the SCR. As long as gate voltage is applied, the SCR converts AC voltage to DC voltage as electricity flows through the SCR. If gate voltage is shut off, no electrical current can flow through the SCR.

in a semiconductor, the action of switching the semiconductor from its nonconducting, or off, state to its conducting, or on state, by applying a negative pulse to its gate terminal.

a silicon-controlled rectifier that can be turned off by applying current to its gate. GTO-SCRs are mainly used for direct-current switching because turnoff can be achieved in a fraction of a microsecond. See silicon-controlled rectifier.

to cause to come together, such as oil from several wells.

the process of bringing oil, gas, or both from a well or wells in a field to a point for delivery to a pipeline or other transporting system.

a pipeline, usually of small diameter, used to move crude oil or gas from the field to a main pipeline.

a central point where there is the accessory equipment for delivering a clean and salable product to the market or to another pipeline.

the pipelines and other equipment needed to transport oil, gas, or both from wells to the gathering station. An oil gathering system includes oil and gas separators, emulsion treaters, gathering tanks, and similar equipment. A gas gathering system includes regulators, compressors, dehydrators, and associated equipment.

General American Transportation Corporation.

1. the diameter of a bit or the hole drilled by the bit. 2. a device (such as a pressure gauge) used to measure some physical property. 3. in electrical circuits, a measure of the diameter (thickness) of the wire or other device that conducts electricity through a circuit or from one point to another. In general, gauges for wire conductors range from 24 to 4/0 (0000). Some common sizes are 6, 12, and 16 with 6-gauge wire being larger in diameter than 16-gauge wire. See American wire gauge. v: to measure size, volume, depth, or other measurable property.

the outside edges of a bit; those portions of a bit that contact the wall of the hole or parallel the wall of the hole.

a valve that activates or isolates a pressure measuring gauge.

the teeth or tungsten carbide inserts in the outermost row on the cones of a bit, so called because they cut the outside edge of the hole and determine the hole’s gauge or size. Also called heel teeth.

a glass tube or metal housing with a glass window that is connected to a vessel to indicate the level of the liquid contents.

the lidded opening in the top of an oil or oil product storage tank through which gauging and sampling operations are carried out.

the housing of an automatic tank gauge. It may include the indicator and the transmitter.

the distance from the gauge, or reference, point from the bottom of a tank to a gauge, or reference, point at the top of the tank, usually on the hatch. On marine vessels, the measurement must be made when the vessel is on even keel.

the heaviest wall casing section of the string, usually located just below the preventers or tree.

small-diameter pipes leading from an orifice fitting to a bellows in a flow recorder. They allow gas pressure to be exerted on the bellows so that the pressure drop across the orifice plate can be recorded.

the vertical distance from the reference point on the gauge hatch to the bottom of the tank or to the datum plate.

a vertical pipe that extends from the gauge hatch to the bottom of the tank or to the datum plate.

1. the point at which a tape is lowered and read on a tank, usually at the rim of the hatch, manway, or expansion dome. 2. a point to which all subsequent measurements are related. 3. the point from which the reference height is determined and from which the ullages/innages are taken.

1. the amount of pressure exerted on the interior walls of a vessel by the fluid contained in it (as indicated by a pressure gauge). It is expressed in pounds per square inch gauge or in kilopascals. Gauge pressure plus atmospheric pressure equals absolute pressure. 2. pressure measured relative to atmospheric pressure considered as zero.

a cylindrical metal ring used to guide, and centralize, packers or tools inside casing.

a phenomenon in which the outside areas (the gauge areas) of a bit become worn and rounded by an abrasive formation.

the outside surfaces of the outermost rows of teeth on a bit. They determine the diameter or gauge of the hole to be drilled.

running of a gauge on tubing or slickline to verify casing dimensions.

the configuration or shape of the teeth in the outermost row of teeth on a bit.

a pipeline representative for the sale or transfer of crude oil from the producer to the pipeline. He or she samples or tests the crude oil to determine quantity and quality and uses a calibrated, flexible-steel tape with a plumb bob at the end to measure the oil in the tank.

a graduated weight used with a graduated tape to measure the height of the liquid in a storage tank. The weight of the bob keeps the tape taut in order to ensure a correct reading of the liquid level.

a graduated, metal, nonsparking, noncorrosive measuring tape used with a gauger’s bob to measure the height of the liquid in a storage tank.

etermining the liquid level of a tank so that its volume can be calculated. Usually done by lowering a weighted graduated steel tape through the tank roof and noting the level at which the oil surface cuts the tape when the weight gently touches the tank bottom. It can also be done by measuring the distance between liquid height and a reference point and subtracting the distance from the gauge height to determine liquid height.

the opening in a tank or other vessel through which measuring and sampling are performed.

a small section of pipe in the top of a tank through which a tank may be gauged.

tables prepared by computers to show the calculated number of barrels or cubic metres for any given depth of liquid in a tank. Sometimes called strapping tables.

a metal tape used to measure the depth of liquid in a tank.

gas-cut; used in drilling reports.

Gulf Cooperation Council.

gas-cut mud; used in drilling reports.

a density log in which a gamma ray log, a Densilog, and a caliper log are recorded simultaneously.

germanium.

a toothed wheel made to mesh with another toothed wheel.

a rotary pump that moves fluid by means of two contrarotating, meshing gear wheels. The teeth of one wheel mesh with the spaces between the teeth of the other wheel. The fluid enters one side of the pump, is forced through by the moving gears, and is discharged on the other side.

see gear reduction unit.

a gear or series of gears that mesh with other gears in a machine and the purpose of which is to reduce the speed of the machine’s output shaft or wheel.

a system consisting of several toothed wheels (gears) that, when manipulated (shifted) by an operator, reduces or increases the speed of a member being driven by the gears.

see rack-and-pinion gear.

a semisolid, jellylike state assumed by some colloidal dispersions at rest. When agitated, the gel converts to a fluid state. Also a nickname for bentonite. v: to take the form of a gel; to set.

cement or cement slurry that has been modified by the addition of bentonite.

a measure of the ability of a colloidal dispersion to develop and retain a gel form, based on its resistance to shear. The gel, or shear, strength of a drilling mud determines its ability to hold solids in suspension. Sometimes bentonite and other colloidal clays are added to drilling fluid to increase its gel strength.

see clabbered.

one of several companies that lease rail cars, such as oil tank cars, to American and European railroads. Based in Chicago, Illinois, GATX was founded in 1898. Besides rail cars, the company also leases locomotives, as well as industrial and marine equipment.

money spent in operating a business (rent, salaries, telephone charges, etc.) that is not directly associated with production of goods or services.

a portion of the United States Occupational Safety and Health Act (Federal OSHA) that states: (1) Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees. (2) Each employer shall comply with occupational safety and health standards promulgated under this act. (3) Each employee shall comply with occupational safety and health standards and all rules, regulations, and orders issued pursuant to this Act which are applicable to his own actions and conduct.

any law relating to the pressure, temperature, or volume of a gas.

a plot of calibration coefficient versus a modified expression of Reynolds number.

a compilation of guidelines for financial accounting. GAAP sets down the standards, conventions, and rules accountants should follow when they record and summarize transactions and when they prepare financial statements.

a machine that changes mechanical energy into electrical energy in the form of direct current. Compare electric motor.

an identification number required for producers of hazardous or acute hazardous waste that exceed EPA minimums under RCRA.

study of the relative and absolute abundances of the elements of the earth and the physical and chemical processes that have produced their observed distributions.

either of two points that lie at either end of an imaginary line drawn through the rotational axis of the earth; one is the North Pole and the other is the South Pole. Compare magnetic pole.

the hypothetical surface of the earth that coincides everywhere with mean sea level. The geoid effectively smoothes out the irregularities in the earth’s surface and is useful for accurate determination of the earth’s gravity field at various locations.

the long periods of time dealt with and identified by geology. Geologic time is divided into eras (usually Cenozoic, Mesozoic, Paleozoic, and Precambrian), which are subdivided into periods and epochs. When the age of a type of rock is determined, it is assigned a place in the scale and thereafter referred to as, for example, Mesozoic rock of the Triassic period.

the relating of subsurface information obtained from one well to that of others.

a scientist who gathers and interprets data pertaining to the rocks of the earth’s crust.

trade name for a patented device that automatically records the rate of penetration and depth during drilling.

the science of the physical history of the earth and its life, especially as recorded in the rocks of the crust.

one of the features that, taken together, make up the form of the surface of the earth.

an instrument placed on the surface that detects vibrations passing through the earth’s crust. It is used in conjunction with seismography. Geophones are often called jugs. See seismograph.

measurement of the physical properties of the earth to locate subsurface formations that may contain commercial accumulations of oil, gas, or other minerals; to obtain information for the design of surface structures; or to make other practical applications. The properties most often studied in the oil industry are seismic characteristics, magnetism, and gravity.

one who studies geophysics.

the physics of the earth, including meteorology, hydrology, oceanography, seismology, vulcanology, magnetism, and radioactivity.

abnormally high pressure exerted by some subsurface formations. The deeper the formation, the higher the pressure it exerts on a wellbore drilled into it.

impermeable shales, highly compressed by overburden pressure, that are characterized by large amounts of formation fluids and abnormally high pore pressure.

a science dealing with the earth—geology, physical geography, geophysics, geomorphology, geochemistry.

the pressure to which a formation is subjected by its overburden. Also called ground pressure, lithostatic pressure, rock pressure.

the change in geostatic pressure per unit of depth in the earth.

to drill a hole in a desired direction; directional and horizontal wells require geosteering to keep them on course and at the desired angle. See geosteering.

the act of drilling a hole in a desired direction; directional and horizontal wells require geosteering to keep them on course and at the desired angle.

a computerized model of drilling the well using real-time log information. See geosteering.

a great downward folding in the earth’s crust. See syncline.

pertaining to heat within the earth.

the boring of a well into a subsurface layer of rock that is very hot or into a rock layer that contains steam or hot water. Once a geothermal well is completed, the heat or the hot water or steam is used to generate electricity. See geothermal reservoir.

the increase in the temperature of the earth with increasing depth. It averages about 1°F per 60 feet (1°C per 18.3 metres), but may be considerably higher or lower.

1. a subsurface layer of rock containing steam or hot water that is trapped in the layer by overlying impermeable rock. 2. a subsurface layer of rock that is hot but contains little or no water. Geothermal reservoirs are a potential source of energy.

a brittle, silvery-gray metallic element in the carbon family. It is a rare metal used in semiconductors, alloys, and glass.

see safety slide.

see safety slide.

to set tools in casing.

ground fault circuit interrupter.

greenhouse gases.

1 billion (1,000,000,000) ohms. Sometimes expressed as 1,000 megohms or 109 ohms.

trade name for asphaltum mined, manufactured, or marketed by or for American Gilsonite Company.

a mechanical frame that permits an object mounted in it to remain in a stationary or near-stationary position regardless of movement of the frame. Gimbals are often used offshore to counteract undesirable wave motion.

generator identification number.

a pole (usually single) with guy wires and used with block and tackle to hoist equipment. On a drilling rig, the gin pole is typically secured to the mast or derrick above the monkeyboard.

a truck equipped with hoisting equipment and a pole or arrangement of poles for use in lifting heavy machinery.

one of the horizontal braces between the legs of a derrick.

ground level; used in drilling reports.

a device used to form a seal around a reciprocating or rotating rod (as in a pump) to prevent fluid leakage. Specifically, the movable part of a stuffing box by which the packing is compressed. See stuffing box.

material placed around a gland to effect a seal around a reciprocating or rotating rod.

a threaded device the sides of which are arranged so that a wrench can be fitted onto them and used to retain the gland packing in place around a rod. See gland packing.

a sub with a glass blockage in the bore, used to isolate a surge chamber in gravel packing or perforation cleaning operations.

a global navigation satellite system (GNSS) developed by the U.S. Department of Defense and managed by the United States Air Force. It uses a constellation of satellites that transmit precise microwave signals that allow GPS receivers to determine their current location, time, and velocity.

see valve.

in paint technology, the visual impression created by the reflecting properties of a painted surface.

a small electric heating element placed inside a diesel engine cylinder to heat the air and to make starting easier.

gas-liquid-ratio.

a group of compounds used to dehydrate gaseous or liquid hydrocarbons or to inhibit the formation of hydrates. Glycol is also used in engine radiators as an antifreeze. Commonly used glycols are ethylene glycol, diethylene glycol, and triethylene glycol.

a cylinder consisting of several perforated trays with bubble caps mounted over the perforations and functioning as a part of a glycol dehydration system. See glycol dehydrator.

a process in which the feed gas water content is lowered by treating it with a circulating stream of glycol to remove moisture to meet the water dew point. The cryogenic cooling process is used to control the gas hydrocarbon dew point.

a processing unit used to remove all or most of the water from gas. A glycol unit usually includes an absorber, in which the wet gas is put into contact with glycol to remove the water, and a reboiler, which heats the wet glycol to remove the water from it so that it can be recycled.

a component in the contactor of a glycol dehydration unit that recovers any glycol that has gotten past the mist extractor.

an absorber contactor dehydration system in which glycol is regenerated in the reboiler and circulated back to the absorption tower, where it contacts the natural gas and removes water as well as hazardous air pollutants.

a pump that uses the pressure of glycol and entrained gas from the contactor to circulate regenerated glycol from the storage tank to the contactor.

a process that uses a solution comprising 10 to 30 percent monoethanolamine, 45 to 85 percent glycol, and 5 to 25 percent water for the simultaneous removal of water vapor, H2S, and CO2 from gas streams.

a system in which glycol is used for water dew-point control and the propane refrigeration system is used for hydrocarbon dew-point control.

General Motors Corporation; a manufacturer of two-stroke-cycle diesel engines used in the petroleum industry.

metacentric height; the abbreviation is used mainly in buoyancy, stability, and trim calculations for offshore floating rigs.

a hydraulic starter motor manufactured by General Motors (GM) that uses hydraulic fluid (light oil) to power a relatively small motor attached to the diesel engine. To start the diesel, the operator activates the Hydrostarter which turns over (moves) the diesel’s pistons. As the pistons move, pressure and heat build up in the diesel’s cylinders and the diesel starts.

to lower the drill stem, the tubing, the casing, or the sucker rods into the wellbore.

1. a device that is inserted into a pipeline for the purpose of cleaning; a line scraper. Also called a pig. 2. a device that is lowered into the borehole of a well for various purposes such as enclosing surveying instruments, detonating downhole explosive devices, and the like. v: to drop or pump a device down the borehole, usually through drill pipe or tubing.

the southern part of the supercontinent Pangaea, comprising the future land masses of South America, Africa, Antarctica, Australia, and India.

pertaining to a well in which production of oil has decreased and production of water has increased (e.g., “the well has gone to water”).

see merchantable title.

1. the curved connection between the rotary hose and the swivel or top drive. 2. any curved length of pipe that serves as a connection between one conduit to another. See swivel, top drive.

gas-oil ratio.

finely abraded material occurring between the walls of a fault as the result of grinding movement.

any device that limits or controls the speed of an engine.

Gas Processors Association.

grains per gallon; parts per million equals grains per gallon ×  17.1.

1. gallons per minute when referring to rate of flow. 2. gallons per thousand cubic feet when referring to natural gas in terms of chromatograph analysis or theoretical gallons.

Gas Processors Suppliers Association.

gray; used in drilling reports.

in sampling petroleum and petroleum products, a small sample, usually 1.5 millilitres (0.05 ounce), obtained by the probe and sampler in an automatic sampling system. Several grabs constitute a sample.

sample obtained by collecting loose solids in equal quantities from each part or package of a shipment and in sufficient quantity to be characteristic of all sizes and components.

a block of the earth’s crust that has slid downward between two faults. Compare horst.

a flowing stream that is stable, or in balance with its average load. It is just steep enough to carry out of its basin the amount of sediment brought in during an average-flow year.

a casing string made up of several weights or grades of casing and designed to take into account well depth, expected pressures, and weight of the fluid in the well. Also called mixed string.

most present-day seamless drill pipe falls into one of four American Petroleum Institute (API) grades. (1) E-75, with a minimum yield strength of 75,000 psi (517,125 kilopascals-kPa), a maximum yield strength of 105,000 psi (723,975 kPa), and a minimum tensile strength of 100,000 psi (689,500 kPa); (2) X-95, with a minimum yield strength of 95,000 psi (655,025 kPa), a maximum yield strength of 125,000 psi (861,875 kPa), and a minimum tensile strength of 105,000 psi (723,975 kPa); (3) G-105, with a minimum yield strength of 105,000 psi (723,975 kPa), a maximum yield strength of 135,000 psi (930,825 kPa), and a minimum tensile strength of 115,000 psi (792,925 kPa); and (4) S-135, with a minimum yield strength of 135,000 psi (930,825 kPa), a maximum yield strength of 165,000 psi (1,137,675 kPa), and a minimum tensile strength of 145,000 psi (999,775 kPa). V-150 is a non-API, but higher strength, grade. It has a minimum yield strength and a tensile strength of 150,000 psi (1,034,250 kPa).

ascending or descending with a uniform slope. The rate of change of temperature or pressure.

the process of providing a smooth and even work area to facilitate the movement of equipment onto and along a right-of-way. Grading entails leveling, cutting, and filling.

see uniformitarianism.

the section of reduced cross-sectional area at the top and/or bottom of an open tank prover. It has visible graduations to enable measuring small volumes.

an open tank prover with one or two graduated necks. See graduated neck.

law that states that the rate of diffusion of a gas is inversely proportional to the square root of its density.

a unit of measure for the strength, or concentration, of a solution. It is based on a unit of weight called the grain, which equals 0.002285 ounce, or 0.0648 gram. One grain per gallon equals 0.058479 part per million.

a unit of metric measure of mass and weight equal to 1/1,000 kilogram and nearly equal to 1 cubic centimetre of water at its maximum density.

see molecular weight.

an igneous rock composed primarily of feldspar, quartz, and mica. It is the most common intrusive rock—that is, it originally solidified below the surface of the earth. Its rock crystals are easily seen by the eye.

a person to whom property is conveyed. Compare grantor.

clause in an oil and gas lease that specifies the rights and interests granted by the lessor to the lessee. Such rights usually involve searching and drilling for, then producing, oil and gas.

a person who conveys property. Compare grantee.

a soft, black, shiny mineral of pure carbon produced when hydrocarbons are subjected to high temperatures and pressures. Used in pencils and crucibles, as a lubricant, and in atomic-energy plants to control the release of radiation from uranium fuel.

a mechanism that is fitted into an overshot to grasp and retrieve fish from the borehole. The interior of a grapple is wickered to engage the fish. See basket grapple, spiral grapple.

a refinery built from the ground up, as opposed to one to which an addition or a modification has been made.

see water outlet.

an open grid assembly of metal bars, in which the load bearing bars, running in one direction, are spaced by a rigid attachment to cross bars running perpendicular to the bearing bars or by bent connecting bars extending between the bearing bars. Grating often serves as flooring or decking to provide access to various areas on the offshore installation.

sand or glass beads of uniform size and roundness used in gravel packing.

a mass of very fine gravel placed around a slotted liner in a well. See gravel packing.

a method of well completion in which a slotted or perforated liner, often wire-wrapped, is placed in the well and surrounded by gravel. If open hole, the well is sometimes enlarged by under­reaming at the point where the gravel is packed. The mass of gravel excludes sand from the wellbore but allows continued production.

to place a slotted or perforated liner in a well and surround it with gravel. See gravel packing.

a packer used for the well completion method of gravel packing.

(pronounced “tower”) the shift of duty on a drilling rig that starts at midnight. Sometimes called the morning tour.

1. an instrument used to detect and measure minute differences in the earth’s gravitational pull at different locations to obtain data about subsurface formations. 2. a device for measuring and recording the density or specific gravity of a gas or liquid passing a point of measurement.

the weight, or density, of a substance. See relative density.

the survey made with a gravimeter.

the force acting upon objects on earth, where the force is the product of the object’s mass, and the acceleration of gravity is at 32 ft/sec/sec. Measured in units of pounds, grams, etc.

also called a densimeter. See gravimeter.

1. the attraction exerted by the earth’s mass on objects at its surface. 2. the weight of a body. 3. an expression of fluid weight stated in degrees of API gravity. See API gravity, relative density, specific gravity.

anchor type that achieves its holding capacity mainly through the weight and friction of its lower surface with the seafloor.

in marketing, the checking of the gravity of the fuel at the terminal.

a double index scale against which a fixed reference pointer may be moved to correct for variations in gravity from a base point computed for water at 60°F. The compensator is marked in both specific gravity and API gravity units.

the difference in density between the water and the oil in an oilfield emulsion. The greater the gravity differential, the easier it is to break the emulsion.

the movement of fluids in a reservoir resulting from the force of gravity. In the absence of an effective ­water or gas drive, gravity drainage is an important source of energy to produce oil, and it may also supplement other types of natural drive. Also called segregation drive.

the tendency of reservoir fluids to separate into distinct layers according to their respective densities. For example, water is heavier than oil; therefore, water injected during waterflooding will tend to move along the bottom portion of a reservoir.

an exploration method in which an instrument that measures the intensity of the earth’s gravity is passed over the surface or through the water. In places where the instrument detects stronger- or weaker-than-normal gravity forces, a geologic structure containing hydrocarbons may exist.

a modified binary code in which sequential numbers are represented by expressions that differ only in one bit. Because the expressions differ by only one bit, errors are minimized.

see inside blowout preventer.

a sandstone that contains more than 15 percent silt and clay, and whose grains tend to be angular and poorly sorted.

a device on a machine that is designed to accept the hose of a grease gun so that grease can be added to the part in need of lubrication.

a surface device used in pressure control for slickline. See lubricator.

sample obtained by scooping or dipping a quantity of soft or semiliquid material, such as grease, from a package so that the material on the scoop or dipper is representative of the material in the package.

when essentially water-insoluble greasy materials (e.g., emulsi-fiers, lubricants) separate out of drilling fluids.

the path on the surface of a sphere-type tank defined by the intersection of a plane surface and including the center of the sphere. Compare equatorial circumference.

raw, untreated gas; gas as it leaves the well and before it enters any field or other treating facilities.

a process whereby the earth’s atmosphere retains long-wave radiation. The atmosphere works in much the same way as the glass panes of a greenhouse.

gases in the atmosphere that absorb and hold heat. GHCs in earth’s atmosphere include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. GHCs affect the temperature of the earth because they retain heat from the sun that falls on the earth during the day—that is, GHCs prevent the escape of some of the heat that occurs after the sun goes down; indeed, without this heat retention, earth’s surface would be, on average, about 59 degrees F (33 degrees C) cooler.

a sand that contains considerable quantities of glauconite, a greenish mineral composed of potassium, iron, and silicate, which gives the sand its color and name.

a free-running propeller mounted on or near the shaft-driven main propeller of a ship or tanker ship. The Grem vane wheel turns like a windmill because of the high-speed flow of water created by the main propeller. A GVW improves efficiency and thus can increase a ship’s speed without additional power.

in diamond drilling bits, a pattern of setting diamonds in which the manufacturer spreads them evenly over the cutting surface (the nose) of the bit. Compare circle plot.

(obsolete) kelly; kelly joint.

term that expresses the effect of a paint’s not totally obscuring the underlying surface.

to test for the presence of water in oil by use of a centrifuge.

see centrifuge.

in pipeline construction, the process of cleaning pipe ends of dirt, rust, mill scale, or solvent to prepare them for welding. Grinding and buffing tasks are accomplished with power hand tools such as wire brushes and buffers.

see wire rope grip.

green; used in drilling reports.

gamma-ray-neutron (a well log).

1. the depression in a sheave (pulley) into which wire rope seats as the wire rope moves over the sheave. 2. on a drawworks drum, one of several depressions on the surface of the drum around which the wire rope drilling line is wrapped. The grooves keep the wire rope from wrapping unevenly across the drum.

in measuring grooves of a sheave, the radius of a circle that fits inside a groove. Used to determine wear on wire rope.

a term applied to grated deck flooring on offshore installations that refers to the total area of the flooring; gross area includes areas of grating that are removed to clear obstructions or to allow pipe, ducts, columns, and the like to pass through the grating. Compare net area.

total energy use, including electrical system energy losses.

the number of kilojoules (Btus) evolved by the complete combustion, at constant pressure, of 1 standard cubic metre of gas, with all of the water formed by the combustion reaction being condensed to the liquid state.

in accounting, the total revenue received from sales of services or goods before deductions or allowances are subtracted. Deductions and allowances include such items as rent, cost of goods sold, and taxes. Also termed gross revenue.

the indicated throughput corrected only for meter performance (i.e., by multiplying by the meter factor).

the total volume of all petroleum liquids and sediment and water, excluding free water, at observed temperature and pressure.

the total production of oil from a well or lease during a specified period of time.

the total volume of a ship’s interior, measured in tons (units of 100 ft3 or 2.83 m3).

see gross income.

the total volume of all petroleum liquids and sediment and water, excluding free water, corrected by the appropriate temperature correction factor (Ctl) for the observed temperature and API gravity, relative density, or density to a standard temperature such as 60°F or 15°C, and also corrected by the applicable pressure correction factor (Cpl) and meter factor.

the total weight of all petroleum liquids and sediment and water (if any), excluding free water. It is determined by applying the appropriate weight conversion factors to the gross standard volume.

the interior capacity of a ship or a mobile offshore drilling unit. The capacity is expressed in tons, although the actual measurement is in volume, 1 ton being equivalent to 100 cubic feet of volume. This rule holds for measuring ship capacity for U.S. maritime purposes. All principal maritime governments have their own rules describing how tonnage is to be measured.

the total weight of a truck or other carrier when it is loaded with goods.

the total amount of liquid in a storage tank excluding any adjustments for S&W, temperature, or density. Compare net volume.

full well stream volume, including all natural gas plant liquid and nonhydrocarbon gases, but excluding lease condensate. Also includes amounts delivered as royalty payments or consumed in field operations.

a working-interest owner’s total ownership in production, before deduction of related royalty, overriding royalty, or production payment interests.

a conducting path, intentional or accidental, between an electric circuit or equipment and the earth, or a conducting body serving in place of the earth. v: to connect electrical equipment to earth or to a conducting body, which serves in place of the earth.

see deadman.

in cathodic protection, an interconnected group of impressed-current anodes that absorbs the damage caused by generated electric current.

a wireline sheave, or pulley, that is fastened to the ground anchor and that changes a horizontal pull on a wire-line to a vertical pull (as in swabbing with a derrick over a well). See block.

the mooring chain part that is laid on the seafloor under normal conditions. It may lift off the seafloor in extreme conditions.

a fast-acting circuit breaker that senses very small ground fault currents and which breaks the circuit when it detects such faults.

in an electric circuit, a device that senses very small ground fault currents that could flow through the body of a person standing on damp ground while touching a live conductor.

see geostatic pressure.

water that seeps through soil and fills pores of underground rock formations; the source of water in springs and wells.

a mortar-like material used to seal between objects. v: to force sealing material into a soil, sand, or rock formation to stabilize it.

an active fault that continues to slip while sediments are being deposited, causing the strata on the downthrust side to be thicker than those on the other side. Also called rollover fault.

gross registered tonnage.

gas sub-cooled process.

gas surge tank.

gate-controlled silicon-controlled rectifier.

a naturally occurring hydrophilic polysaccharide derived from the seed of the guar plant. The gum is chemically classified as a galactomannan. Guar gum slurries made up in clear fresh or brine water possess pseudoplastic flow properties.

the minimum amount of royalty income a royalty owner is to receive under the terms of the lease agreement, regardless of the royalty owner’s share of actual proceeds from the sale of production.

a metal shield placed around moving parts of machinery to lessen or avoid the chance of injury to personnel. In the oilfield, guards are used on equipment such as belts, power transmission chains, drums, flywheels, and drive shafts.

a focused system designed to measure the true formation resistivity in wellbores filled with salty mud. Current is forced by guard electrodes to flow into the formation. Also called Laterolog™.

person appointed by a court of competent jurisdiction for the purpose of managing property and rights for another person who is considered incapable of managing for himself or herself—for example, a minor child, a mentally ill person, or someone judged mentally incompetent.

a railing for guarding against danger or trespass. On a drilling or workover rig, for example, guardrails are used on the rig floor to prevent persons from falling; guardrails are also installed on the mud pits and other high areas where there is any danger of falling.

in pipeline construction, the means by which a river crossing stays on course. Frequently computerized, guidance systems may be based on information gathered by pendulums, which determine inclination; gyroprobes, which are sensitive to drift and bearing; and sonar. Lasers are also used to guide crossing.

see permanent guide base, temporary guide base.

the petrified remains of plants or animals, useful for correlation and age determination of the rock in which they were found.

see conical funnel.

a device, usually in the form of a cylindrical vertical tube, used in floating roof tanks to prevent rotation of the roof.

on some top drives, the steel tracks on which the top-drive unit travels up and down when the driller raises or lowers the traveling block. The rails also keep the unit from turning when its motor rotates the drill stem. Compare torque track, torque tube. See also top drive.

a cylindrical metal ring used to guide packers past casing obstructions.

1. a short, heavy, cylindrical section of steel filled with concrete and rounded at the bottom, which is placed at the end of the casing string. It prevents the casing from snagging on irregularities in the borehole as it is lowered. A passage through the center of the shoe allows drilling fluid to pass up into the casing while it is being lowered and allows cement to pass out during cementing operations. Also called casing shoe. 2. a device, similar to a casing shoe, placed at the end of other tubular goods.

see guideline.

1. one of usually four lines attached to the temporary guide base and permanent guide base to help position equipment (such as blowout preventers) accurately on the seafloor when a well is drilled offshore from a floating vessel. Guidelines are normally used to drill in water depths of 5,000 feet (1,500 metres) or less. 2. on a spinning chain, a piece of fiber rope (soft line) that is attached to the end of the chain that is wrapped around the tool joint. When the makeup cathead pulls the chain off the drill pipe, a rotary helper uses the guideline to control the chain’s movement. Note that spinning wrenches have replaced spinning chains on most modern drilling rigs.

a system of cables (wire ropes), pulleys (sheaves), and pressurized piston-and-cylinder assemblies that maintain an upward tension on the guidelines to keep them taut and to compensate for rig heave (up-and-down movement). See guideline.

lines, usually four, attached to the temporary guide base and permanent guide base to help position equipment (such as blowout preventers) accurately on the seafloor when a well is drilled offshore from a floating vessel.

association of Persian Gulf nations—Bahrain, Kuwait, Qatar, Oman, Saudi Arabia, United Arab Emirates—formed to defend themselves collectively against aggression.

that portion of the Intracoastal Waterway (ICW) in the United States that is located along the coast of the Gulf of Mexico. The ICW runs for about 3,000 m (4,800 km) along the Atlantic and Gulf coasts of the US. It runs from Brownsville, TX to the Manasquan River in New Jersey. Natural inlets, rivers, bays, and sounds make up parts of the waterway and manmade canals make up the rest. The waterway provides a navigable route for barges and other shallow-draft vessels and therefore allows such vessels to avoid hazards of the open sea.

warm ocean current that flows north from the Gulf of Mexico along the eastern U.S. coast to an area off the southeastern coast of Newfoundland.

any hydrophilic plant polysaccharides or their derivatives that, when dispersed in water, swell to produce a viscous dispersion or solution. Unlike resins, they are soluble in water and insoluble in alcohol.

any relatively sticky formation (such as clay) encountered in drilling.

a settling tank used to separate oil and water in the field. After emulsified oil is heated and treated with chemicals, it is pumped into the gun barrel, where the water settles out and is drawn off, and the clean oil flows out to storage. Gun barrels have largely been replaced by unified heater-treater equipment, but are still found, especially in older or marginal fields. Also called a wash tank.

to agitate the drilling fluid in a pit by means of a mud gun, electric mixer, or agitator.

to create holes in casing and cement set through a productive formation. A common method of completing a well is to set casing through the oil-bearing formation and cement it. A perforating gun is then lowered into the hole and fired to detonate high-powered jets or shoot steel projectiles (bullets) through the casing and cement and into the pay zone. The formation fluids flow out of the reservoir through the perforations and into the wellbore. See jet-perforate, perforating gun.

trade name for a cement-sand mixture used to seal pipe against air, moisture, and corrosion damage.

the collection of dirt, paraffin, oil, mill scale, rust, and other debris that is cleaned out of a pipeline when a scraper or a pig is put through the line.

a slurry in crude or diesel oil containing any of the following materials or combinations: bentonite, cement, attapulgite, and guar gum (never with cement). Used primarily in combating lost circulation.

a mixture of diesel oil and bentonite that is sometimes used to seal a lost circulation zone.

a bentonite and diesel oil mixture that is pumped down the drill pipe and into the annulus to mix with drilling mud. The stiff, puttylike material is squeezed into lost circulation zones to seal them.

the intersection of the deck plating with the side shell plating on a ship.

an oilwell that has come in with such great pressure that the oil jets out of the well like a geyser. In reality, a gusher is a blowout and is extremely wasteful of reservoir fluids and drive energy. In the early days of the oil industry, gushers were common and many times were the only indication that a large reservoir of oil and gas had been struck. See blowout.

a wireline attached to a mast, derrick, or offshore platform to stabilize it. See load guy line, wind guy line.

a buried weight or anchor to which a guy line is attached. See deadman.

a supporting rope which maintains a constant distance between the points of attachment to the two components connected by the rope.

a rope or cable used to steady a mast or pole.

a compliant offshore drilling platform used to drill development wells. The foundation of the platform is a relatively lightweight jacket on which all equipment is placed. A system of guy wires anchored by clump weights helps secure the jacket to the seafloor and allows it to move with wind and wave forces. See platform rig.

the system of guy lines and anchors used to brace a rig.

1. Grem vane wheel. 2. Gross vehicle weight.

(slang) gypsum.

drilling mud that is treated with gypsum to provide a source of soluble calcium in the filtrate to obtain desirable mud properties for drilling in shale or clay formations.

a naturally occurring crystalline form of calcium sulfate in which each molecule of calcium sulfate is combined with two molecules of water. See anhydrite, calcium sulfate.

analyses of readings and plots of surveys conducted with gyroscopic surveying instruments.

a compass card linked to a gyroscope in a gyroscopic multishot instrument. Unlike a magnetic compass, a gyrocompass is not affected by the earth’s magnetic field.

a wheel or disk mounted to spin rapidly about one axis but free to rotate about one or both of two axes perpendicular to each other. The inertia of the spinning wheel tends to keep its axis pointed in one direction regardless of how the other axes are rotated.

a device that indicates direction without relying on a magnetic compass. It finds true north by using a gyroscope and is therefore not influenced by external magnetic fields such as those created by iron bearing metals. Gyroscopic compasses are widely used in directional drilling to determine the direction of the borehole. See gyroscope, gyroscopic surveying instrument.

a photographic device used to determine direction and angle at which a wellbore is drifting off vertical; especially useful for directional surveys in or near cased wells or down the length of a drill string. Several survey readings are taken at preset intervals while drawn up the drill string. Readings are not affected by magnetic irregularities caused by casings or other ferrous metals.

a device used to determine direction and angle at which a wellbore is drifting off vertical. The gyroscopic single-shot instrument takes a single reading and is not affected by magnetic irregularities caused by casings or other ferrous metals.

see gyroscopic surveying instrument.

a device used to determine direction and angle at which a wellbore is drifting off the vertical. Unlike magnetic surveying instruments, a gyroscopic instrument reads true direction and is not affected by magnetic irregularities that may be caused by casing or other ferrous metals. See directional drilling, directional survey.

the righting arm (or lever).