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ABANDON – To permanently plug and salvage equipment from a well. A well is ordinarily abandoned if it is a dry hole or has ceased to produce in commercial quantities for some reason, which condition is believed permanent and beyond repair.

ACIDIZE – To treat a well with acid, largely hydrochloride, to dissolve some limestone or other carbonate material in a producing zone. The object is to enlarge and reopen pores, vugs, and fractures in the zone to increase the flow of oil or gas into the well bore.

AIR DRILLING – Process in which the cleaning of the cuttings from the well bore during the actual drilling of the well is done with air. This type of drilling is normally used where the formations being penetrated are too weak to support the hydrostatic weight of normal drilling fluids.

ANTICLINE – An elongated fold in rock strata in the form of a buried hill. This is a common type of oil and gas reservoir, with oil and gas, being lighter, accumulating in the higher part of the structure above water.

ASSIGNMENT- In law generally a transfer. In oil and gas law usually a transfer of a property interest or of a contract. The most common usage refers to the assignment of an oil and gas lease.

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BAILER – A hollow column of pipe with a dump-valve assembly in the bottom. It is lowered into a well on a wire line to recover drill cuttings, fluids, etc.

BENTONITE – A clay material used in drilling mud. It swells with the addition of water and has a slick feel, both desirable mud properties.

BIT/ROTARY – The cutting tool at the bottom of the drill stem which is rotated to cut, chip, and grind to make hole in rotary drilling. There are several types:

- Fishtail Bit – A rotary bit having chisel-shaped blades and used to drill soft formations.

- Rock-Bit – The most common rotary, having three conical-shaped cutters mounted on polished bearings. The revoking cones have serrated teeth of various design to drill soft and hard rock. Synonym: Roller-Cone Bit.

- Core Bit – A special bit having a hole in the center used to cut rock core as formation is penetrated. The diamond core bit is the most common, using industrial diamonds as the cutting material; several hundred carats may be mounted in a single bit.

BIT/CABLE TOOL – A long steel bar with chisel-shaped bottom edge, operated by percussion to chip and pulverize rock as it is dropped and raised repeatedly in cable-tool drilling.

BOTTOM HOLE PRESSURE – The pressure at the bottom of a well measured in pounds per square inch.

BTU – British Thermal Unit, heat (energy) required at sea level to raise the temperature of one pound of water one degree Fahrenheit.

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CASING – Steel pipe run in a well to “case” or line the hole; purpose is to protect the hole from caving, to prevent entry of fluids from other strata, and permit selective production through perforations. Casing size is specified by internal diameter; size ranges from 4” to 30”.

CASING POINT – The objective depth (either a specified depth or the depth at which a specific zone is penetrated). When reached, the operator makes the decision with respect to running and setting a production string of casing.

CEMENTING – The operation by which a slurry of specially formulated cement is forced through casing and up around its lower end, filling the space between the casing and wall of the hole to a selected height. The purpose is to secure the casing in place and exclude water and formation fluids from the well.

CIRCULATE – To cycle drilling mud, air, or soap down through the drill pipe and up between the drill pipe and wall of the hole to the surface. The term more specifically refers to such cycling for conditioning the well bore while drilling is temporarily suspended; this is often done before hoisting drill pipe in preparation to running casing or logging.

COMPLETED WELL – A well on which drilling and completion operations have been finished; well may be completed as a dry hole, a well capable of producing oil or gas, a salt-water disposal, or other special-purpose well.

COMPLETION OF A WELL – An indefinite term, but including those steps in attempting to bring a well into production after the well has been drilled to total depth through a prospective pay zone. Such steps include running and cementing a production string of casing, perforating, running tubing, acidizing or fracturing, swabbing, etc.

CONTOUR – A line every point of which is the same elevation above or below sea level.

CORE ANALYSIS – Analyzing a core sample for porosity, permeability, water, oil, and gas saturations.

CORING – A way of obtaining additional information about a zone that may contain gas.

CORE SAMPLE – A core barrel is placed at the bottom of the drill string and used for drilling. The center of the cut remains in the string and this material is removed and analyzed both on location and in a laboratory.

CUBIC FOOT OF GAS – Means the volume of gas contained in one cubic foot of space at a standard pressure base of 14.73 pounds per square inch and a standard temperature base of 60 degrees Fahrenheit. Most generally, volumes are recorded in 1000 cubic feet (mcf).

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DAY WORK – In drilling contracts, work paid for at an agreed price per day; usually applicable to coring, drill stem testing, and other operations where normal drilling operations are suspended at the request of the operator.

DECATHERM – A decatherm is 1,000 cubic feet of gas at 1,000 Btu’s. Gas with a high Btu content is generally sold at a higher price i.e. if the price paid for gas is $1.80 per decatherm, and the Btu content is 1,280, the amount paid for the gas per mcf (1,000 cubic feet) amounts to approximately $2.25 per mcf.

DEVELOPMENT WELL – A well drilled within a presently proven productive area of a gas reservoir, as indicated by reasonable interpretation of available data, with the objective of completing in that reservoir. The drilling of development wells involves a lower degree of risk than field extension or exploratory wells because they are reasonably expected to produce gas in paying quantities. Synonym: Field development well.

DIP – The inclination or slope of sedimentary rock strata, expressed in degrees from the horizontal.

DOME – Anticline of more or less circular shape like an inverted bowl.

DRILL COLLAR – A drill pipe which is slightly larger in diameter and much thicker and, therefore, heavier. This pipe is attached to the drill bit and is used to apply weigh control the bit. DRILL PIPE – Extra heavy pipe designed to stand the great torque and corkscrewing effect in applying rotary motion and pressure to a rock bit at depth. Drill pipe comes in 20, 30, and 40 foot lengths in diameters of 2-3/8 to 6-5/8 inches with weight from 6 to 25 pounds per foot. The drill coupling is called a tool joint, specially designed for great strength and quick make up.

DRILL RIG – The drilling apparatus. A rotary rig includes the following components: Derrick or mast, substructure, blowout preventer, drawworks, a system of blocks and steel rope, rotary table and drive, engines, mud pumps, and mud circulating system and/or air compressors and booster pump.

DRILL STEM, DRILL STRING, DRILL COLUMN – The string of drill pipe from the bit at the bottom of a hole to the kelly at the top, carries mud or compressed air down to the bit.

DRY HOLE – A completed well not productive of gas or oil in paying quantities.

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ELECTRIC LOG – An electrical survey which provides a record of certain electrical characteristics of formations traversed by the borehole. An electric survey is made to identify the formations, determine the nature and amount of fluids they contain, and estimate their depth. There are three (3) main curves; (1) The resistivity of induction curve; (2) The S.P. curve, used to determine rock characteristics and some degree of permeability; (3) Differential temperature survey. Electric logs are also valuable for correlation between wells.

EXPLORATORY WELL – A well drilled either: (a) in search of a new as yet undiscovered pool of gas or (b) to greatly extend the limits of a pool. It involves a relatively high degree of risk because it is drilled in a relatively unproven area or to an unproved formation. Exploratory wells may be subclassified as follows: (a) wildcat, drilled in an unproved area; (b) field extension or step out, drilled in an unproven area to extend the proven limits of a field, (c) deep test, drilled within a field area but to unproven deeper zones.

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FERC – Federal Energy Regulatory Commission. The five member regulatory commission within the Department of Energy which replaced the Federal Power Commission in 1977 when the Department of Energy was created by Pub. L. No. 95-91 (Aug. 4, 1977), 42 U.S.C. Sec. 7101 at seq. The new commission has substantially the same regulatory powers as the predecessor commission and has been given additional responsibility for regulating oil pipelines, a function previously allocated to the Interstate Commerce Commission.

FARMOUT – A very common form of agreement between operators, whereby a lease owner not desirous of drilling at the time agrees to assign the lease, or some portion of it (in common or in severalty) to another operator who is desirous of drilling the tract. The assignor in such an arrangement may or may not retain an overriding royalty or production payment. The primary characteristic of the farmout is the obligation of the assignee to drill one or more wells on the assigned acreage as a prerequisite to completion of the transfer to him.

FAULT – A break or fracture zone in rock strata where the layers or rock on one side have slipped downward or laterally relative to the other.

FIELD EXTENSION WELL STEP OUT WELL – A well drilled in semi-proved or unproved area to extend the productive limits of a gas field. It is a class of exploratory well when drilled in an unproved area; where the step out is only a short distance, and within the proven or semi-proven area, it may be considered a development well.

FLOWING WELL – A well that produces gas and/or by natural energy without any form of artificial lift.

FLOWING LINE – The pipe section connecting a producing gas well through the wellhead and associated equipment to the gas meter and gas pipeline.

FLUID DRILLING – Process in which the cleaning of the cuttings from the well bore during the actual drilling of the well is done with fluids.

FORMATION – Sedimentary rock beds deposited continuously and under the same general conditions and of the same geologic age. A group formation consists of an individual bed or group of beds distinct in character and persisting over a fairly large area.

FRAC – A process where a sand bearing fluid penetrates and oil/gas bearing zone in an attempt to increase the zone’s productivity. There have been several new fracturing techniques developed in the last several years which have made some former nonproductive zones productive.

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GAS – Any fluid, either combustible or noncombustible, which is produced in a natural state from the earth and which maintains a gaseous or rarefied state at ordinary temperature and pressure conditions.

GAS PURCHASING CONTRACT – A contract for the sale and purchase of gas entered into by the purchaser and the operator of the well from which the gas is produced. The purchaser may be an interstate or intrastate pipeline company or a gas marketer, purchasing gas from a number of wells for resale to industrial end-users. The gas purchase contract in Appalachia provides for payment to all production proceeds to the operator who then distributes to the royalty interest, overriding royalty interest, and working interest owners.

GEOLOGICAL SURVEY – Field work and study as to geological prospect or area. The study may include information on surface outcrops, the mapping and correlation of subsurface data, aerial photos, etc.

GEOLOGICAL STRUCTURE – A fold, fault or other deformation of the earth’s crust. Common types of geologic structures include: faults, domes, anticlines, monoclines, and synclines.

GEOLOGIST – A scientist whose specialty consists of procurement and interpretation of data pertaining to the earth’s crust. A petroleum geologist (in contrast to a mining or hard-rock geologist) is primarily concerned with sedimentary rocks and the search for traps favorable to the accumulation of oil and gas.

GUN PERFORATING – A well completion method in which holes (perforations) are made through casing and cement sheath into the adjoining formation by the firing of projectiles from a perforating gun.

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HEATER – A piece of equipment often necessary on high pressure gas and distillate wells and used especially in cold weather to prevent hydrates from forming which would hinder the operation of a separator.

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INITIAL POTENTIAL – The production rate reported on the initial completion of a well. This is usually the results of a production test made at the time of completion or shortly thereafter and reported as the amount of gas produced per day under stated flowing conditions. The reported information may or may not reflect the capacity of the well.

ISOPACH MAP – A map showing the variation in thickness of a particular rock bed or formation. An isopach is a line every point of which represents the same thickness of a formation.

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KELLY – The heavy square or hexagonal-shaped steel pipe which is suspended from the swivel and connected to the drill string. The kelly is rotated by a drive bushing in the rotary table and thereby rotates the drill string.

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LEASE BROKER – A person who is in the business of obtaining leases for speculation and resale. He may act on his own or as an agent for others, including oil companies.

LEASE STORAGE TANK – A cylindrical steel tank for the collection and storage of fluids produced from wells on a single lease. Such tanks are calibrated so that by measuring the height of fluid in a tank that number of barrels contained can be determined from a table prepared for that particular tank. Synonyms: stock tank, field tank.

LIMESTONE LIME – A sedimentary rock composed mainly of calcium carbonate.

LOCATION – A well site.

LOCATION DAMAGES – Compensation paid to the surface owner for actual and potential damage to the surface and crops in the drilling and operation of a well.

LOG – See Electric Log. Well Log, and Sample Log. The driller’s log is a running account of events and formations encountered in drilling in chronological order.

LONGSTRING CASING – Run and set for production.

LOST CIRCULATION, LOST RETURNS – An interruption in the circulation of drilling fluid caused by the fluid entering a porous zone, fracture or cavity, preventing the fluid from returning to the surface.

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MCF – Thousand cubic feet. The standard unit for measuring the volume of natural gas.

MUD DRILLING – A heavy liquid used in the rotary drilling process. Mud is circulated down the drill stem, through openings in the drill bit and up the sides of the hole back into the mud pit. Its purpose is to carry drill cuttings to the surface, lubricate the bit and drill stem, plaster the sides of the hole to prevent mud loss and hole caving and to confine high-pressure gasses of liquids to the formations encountered.

MUD PIT – See Slush Pit.

MULTIPLE COMPLETIONS – The completion of a single well in more than one producing horizon or formation simultaneously.

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OFFSET – (1) A location or a well on one lease at a comparable distance from the lease boundary as the closest well or location on an adjoining lease. In a square or checkerboard spacing pattern there are direct offsets and diagonal offsets. (2) An adjoining location or well, whether on the same or a different lease. (3) The distance between offset locations.

OPEN HOLE – The uncased part of a well.

ORRI – overriding royalty. An interest in oil and gas produced at the surface, free of the expense of production, and in addition to the usual landowner’s royalty reserved to the lessor in an oil and gas lease.

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PAY ZONE OR HORIZON – Rock strata constituting a gas reservoir and containing recoverable gas.

PERFORATIONS – Holes made in casing and the surrounding cement sheath through which formation fluids may flow into the well bore. (See gun perforating).

PERMEABILITY – (1) A measure of the ease with which fluids can flow through a porous rock; (2) The fluid conductivity of a porous medium; (3) The ability of a fluid to flow within the interconnected pore network of a porous medium. It is expressed in millidarcies (or darcies).

PETROLEUM – An oily, inflammable liquid consisting of a complex mixture of hydrocarbons.

PETROLEUM ENGINEER – An engineer whose expertise is producing oil and gas. He interprets logs and other available data, makes the decision whether or not to set pipe on a well, sets up the completion procedure, and supervises production.

PINCH OUT – A geologic trap in which a porous permeable rock stratum wedges out between non-permeable layers.

PLUG (AND ABANDON) – To fill a hole with mud and/or cement as required by state regulations in abandoning a well. A cement cap or pipe is left to mark the location. POROSITY – The porous space found within the matrix of the reservoir rock. This porous space is what contains the oil, gas, and water within the zone. The more porosity the zone has, the more fluids it will contain.

POTENTIAL – The actual or calculated ability of a well to produce gas as determined by a well test.

PRODUCING ZONE, HORIZON, RESERVOIR, OR SAND – A rock reservoir (stratum) yielding recoverable gas.

PUMP, SUB-SURFACE – A down-hole pump to artificially lift fluids to the surface. There are three types: (1) Plunger pump operated by sucker rods; (2) Hydraulic pump operated by high pressure liquid; and (3) Bottom-hole centrifugal pump, electrically powered.

PUMP UNIT – Surface pumping equipment driven by a motor. It imparts an up and down motion to a subsurface pump through a string of sucker rods.

PUMPING WELL – A well produced by artificial lift; more specifically, a well produced by means of a subsurface pump.

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RECOMPLETION – Work on a well to re-complete it in a different formation, either deeper or shallower than originally completed. (See work over for the distinction)

REEF– A buildup of limestone in reef form, a type of stratigraphic reservoir.

RESERVOIR, GAS OR OIL – A single common accumulation of gas and/or oil in a porous permeable underground rock strata zone completely separate from other zones.

RESISTIVITY – A measurement of the resistance of rock and its contained fluids to the passage of electrical current. It is a common electric log measurement. As the water contained in rocks is salty to some degree, it is conductive compared to oil and gas, which are not. Thus, the resistivity curve is a possible clue to the existence of petroleum in rock formation.

ROTARY DRILLING – The common method of well drilling involving the cutting of a hole by rotating a bit at the bottom of a column of drill pipe and hydraulically circulating the cuttings to the surface with drilling fluids, air, or soap.

ROTARY TABLE – The chain or gear-driven circular steel equipment on the floor of a drilling rig which is adapted to and turns the kelly (and thus the drill stem) through drive bushings.

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SALT WATER DISPOSAL WELL – A well used for the disposal of salt water by injection into underground formations. Water produced with oil or gas is salty to varying degrees and it must be disposed of in such a way as not to pollute surface streams of freshwater sands.

SAMPLE LOG – A strip chart for a well on which there is a description of the rock characteristics (lithology) from drill cuttings and core samples plotted with depth.

SEPARATOR – A tall cylindrical tank in which gas in solution is separated from the oil.

SET CASING – To run and cement casing in a well.

SETTLED PRODUCTION – Production at a fairly stable, relatively uniform rate with hardly noticeable decline in productive capacity with time.

SKID THE RIG – Move the drilling rig from one location to another with little or no dismantling or equipment.

SOAPING – Term applied to the injection of a solution to the compressed air in an air drilling system to aid the lifting of formation fluids. Also applied to producing wells to allow the free flowing of produced liquids when the gas cannot continue to free flow the fluids by itself.

STABILIZED – When the rate of production of a well remains steady on a given size choke or under given pumping conditions.

STRATIGRAPHIC – Pertaining to rock strata and their characteristics and geometry.

STRATIGRPAHIC TRAP – A reservoir capable of holding gas and limited by non-permeable beds or by a change in the character or continuity of the rock to non-permeable beds.

STRATUM – A distinct bed of sedimentary rock; strata; plural, a series of beds.

STRUCTURAL TRAP – A reservoir formed by a fold or fault structure in the earth’s crust and capable of holding gas.

SUCKER RODS – A string of rods connecting a subsurface pump with the polish rod and pumping unit at the surface.

SURFACE DAMAGES – Compensation paid to the surface owners for damage or potential damage attributable to a well location or lease operation.

SWAB – (1) A rubber cup-shaped devise with a check valve run on a wire line to lift liquid up through pipe in a well during testing, completion, or work over operations; or (2) The swabbing operation.

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TANK BATTERY – Consists of lease storage tanks, a separator, and possibly a water tank.

TRAP – Porous rock strata capable of holding oil gas by structural folding or faulting and/or stratigraphic limitation

TUBING – A string of pipe, normally 3 inches or less in diameter, run inside casing in a well and through which gas is produced. The predominate sizes are 1 ½ and 2 inch diameter.

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WELL LOG – A record reporting the formations penetrated, their depth, rock description, etc.; the location of the well, casing set, completion data, and other pertinent information. A well is required by the state in which drilled (and by the Federal Government if on Federal lands). There are numerous other types of logs run on wells, including electric log, radioactivity log, sample log, caliper log, sonic log, density log, temperature log, and microlog.

WELL PERMIT – State (or Federal) authorization to drill a well.

WELL SPACING – The regulation or specification of the acres per well and distance between the wells as a conservation or economic measure.

WILDCAT – An exploratory well drilled in unproved territory.

WORK OVER – Remedial operations on a well, with the hope of restoring or increasing production from the same zone; includes such work as plugging back, squeeze cementing, reperforation, clean-out, acidizing, etc. A work over to recomplete in another formation is called a recompletion.

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