To cease work on a well which is non-productive, to plug off the well with cement plugs and salvage all recoverable equipment Also used in the context of field abandonment.
Final plugging of wells, and/or permanent dismantling, etc. of a production platform or other installation.
Treatment of oil-bearing limestone or carbonate formations with a solution of hydrochloric acid and other chemicals to increase production. The acid is forced under pressure into the formation where it enlarges the flow channels by dissolving the limestone.
AFE - AUTHORISATION FOR EXPENDITURE
Capital budget prepared by the operator's engineers of the projected costs of drilling the well both dry and successful. If there are other working interests, each partner in the well must sign the AFE before drilling begins.
Annual General Meeting
AMERICAN PETROLEUM INSTITUTE (API)
API is the world's foremost authority on oil industry standards and practices. "API Gravity" is a reference system for the density of crude oils and constituent hydrocarbons.
ANGLE OF DEFLECTION
The angle, in degrees, at which a well is deflected from the vertical by means of a whipstock or other deflecting tool.
The space between the drillstring and the well wall, or between casing strings, or between the casing and the production tubing.
A geological structure sometimes described as a dome or inverted saucer. Such a structure would be an anticline with "four way dip closure" which if covered by an impermeable layer of rock would make a potential oil or gas reservoir. Not all anticlines are this "perfect" shape.
Degrees API, a standard measure of oil density defined by the American Petroleum Institute.
A well drilled as part of an appraisal drilling program which is carried out to determine the physical extent, reserves and likely production rate of a field.
Any system that adds energy to the fluid column in a wellbore with the objective of initiating and improving production from the well. Artificial-lift systems use a range of operating principles, including rod pumping, gas lift and electrical submersible pumps.
Australian Securities and Investments Commission.
Natural gas associated with oil accumulations, which may be dissolved in the oil at reservoir conditions or may form a cap of free gas above the oil.
Australian Stock Exchange Limited.
The conversion of a (smaller) cost-free interest to a (larger) working interest in a well, normally occurring when the original capital investment in the well has been returned (at payout). BACK OFF
In drilling, to pull the drill-string out of, or partly out of, the borehole. To unscrew a joint of drillpipe. To slacken off a line or block. BARREL
A unit of volume measurement used for petroleum and its products (7.3 barrels = 1 ton: 6.29 barrels = 1 cubic metre). BCM
Billion cubic metres (1 cubic meter = 35.31 cubic feet). BBL
Billion cubic feet .BCM
Billion cubic metres (1 cubic metre = 35.31 cubic feet). BCPD
Barrels of condensate per day.BEFORE PAYOUT ("B.P.O.")
The period of time when the capital costs of drilling a well are being recovered from the net revenues generated by production from that well. BFPD
Barrels of fluid per day. BOEPD
Barrels of oil equivalent per day. BONUS
The cash consideration paid to the United States by the successful bidder for a mineral lease. The payment is made in addition to the rent and royalty obligations specified in the lease. BOPD
Barrels of oil per day. BIT
A drilling bit. Those chiefly in use are the steel roller-cutter, and the diamond-insert bit and PDC bit for hard formations, which penetrates by scratching or abrading the rock rather than by crushing or pulverising like the roller bit. There is also the annular diamond-insert core bit, for cutting and retrieving rock samples (in conjunction with a core barrel).BLOW-DOWN
Condensate and gas is produced simultaneously from the outset of production. BLOWOUT
Uncontrolled or uncontrollable release of down hole pressure upward through the well-bore or casing. Although the main danger is fire, the gases are also toxic, and in floating operations a gas blowout may include a threat to the stability of the rig itself. (See Mud)BLOWOUT PREVENTER (BOP)
An emergency shut-off valve installed on the wellhead during drilling or testing of a well, which incorporates hydraulic pipe rams capable of closing the space around the drill pipe against very high pressures.BOTTOMS UP
Circulation of drilling fluid in a well, until the bottom hole mud and cuttings reach the surface.BREAKOUT
Act of unscrewing one section of pipe from another section, particularly when drill pipe is being withdrawn from the well bore. BRIDGE PLUG
A down hole packer assembly used in a well to seal off or isolate a particular formation for testing, acidising, cementing, etc. also a type of plug used to seal off a well temporarily while the wellhead is removed.BRING IN A WELL
Act of completing and bringing a well into production.
A tool for checking casing in a well for deformation before e.g. running drilling tools, which might become stuck, or packers which might leak.CAP ROCK
Impermeable rock overlying an oil or gas reservoir that tends to prevent migration of the reservoir fluids from the reservoir. CAPPED WELL
A well capable of production but lacking wellhead installations and a pipeline connection. CARRIED INTEREST OR NET EARNED INTEREST
The term "carried interest", as usually used in the oil and gas industry, refers in a broad sense to situations wherein an oil and gas venture must "pay out" (i.e. all drilling, developing and operating costs must be recovered out of production) before the owner of the carried interest receives any proceeds from the venture. A common type of carried interest is created where the owner of an undivided share in the working interest under a lease agrees to advance all funds for costs of drilling, developing and operating the property to which the lease applies. In such a situation, the owner or owners of the other undivided shares in the working interest become "carried interests". The person advancing the funds (operator) is said to be "carrying" the other interests in that their respective pro rata shares of the costs of drilling, developing, and operating the property are paid by him and are recoverable by him solely out of their respective pro rata shares of proceeds from oil and gas production. CASH CALLS
Money requested in advance by operator from participants in a well for capital costs. CASING HEAD
Heavy steel fitting that connects the first string of casing and provides a housing for the slips and packing assemblies by which subsequent strings of casing are suspended and the annulus sealed off. CASING POINT
The depth of the lower end of a string of casing.CASING SHOE
A short assembly, typically manufactured from a heavy steel collar and profiled cement interior, that is screwed to the bottom of a casing string. The rounded profile helps guide the casing string past any ledges or obstructions that would prevent the string from being correctly located in the wellbore.CASING STRING
Total feet of casing run in a well. CEMENT ETC.
Cement is used to "set" casing in the well bore and seal off unproductive formations and apertures.CHOKE
An aperture restricting flow in a well or flowline.CHRISTMAS TREE
The manifold, or arrangement of pipework connections and valves which is installed on the wellhead prior to production. As well as outlets for production, the tree will provide for the injection of mud to "kill" the well, and for the insertion of downhole maintenance tools and wirelines.CIRCULATE
Cycling of the drilling fluid through the drill string and wellbore while drilling is temporarily suspended. This is done to condition the drilling fluid and wellbore before drilling proceeds. CLOSE IN
To shut in (temporarily) a well that is capable of production. CLOSURE
Four-way (all round) closure or seal is necessary, over the top and down the gradients on the sides of a potential reservoir, before it can trap or retain hydrocarbons. Closure may be structural as in an anticline, or may be partly due to an impermeable fault, or stratigraphic trapping. COILED TUBING
A long, small diameter pipe flexible enough to be stored on and deployed from a large, truck-mounted roll. Used to replace jointed pipe in certain types of drilling, completion, and workover operations.COMMERCIAL WELL
A well capable of producing profitably.COMPLETION
Installation in a well of production tubing and equipment, wellhead and Christmas Tree.CONDENSATE
Hydrocarbons which are in the gaseous state under reservoir conditions and which become liquid when temperature or pressure is reduced. A mixture of pentanes and higher hydrocarbons. CONING
If an oil well is produced at excessive rates the reduction in reservoir pressure may tend to draw up underlying water towards the well in a cone like shape, like-wise gas can be drawn downwards from an overlying gas cap.CORE/CORE BARREL
A vertical section of reservoir or other rock taken in drilling a well, for detailed study and analysis. In order to retrieve the core as intact as possible, it is cut from the rock by an annular core bit. The central column of rock passes through the centre of the bit and, as the bit cuts deeper, is received by a hollow cylindrical Core Barrel above the bit, where it is retained and protected by a series of rubber baffles. When the bit has cut deep enough to fill the core barrel, it is withdrawn from the hole and the core extracted. In this way the actual sequence of rock strata is preserved.CUTTINGS
Rock chips cut from the formation by the drill bit, and brought to the surface with the mud. Used by geologists to obtain formation data.
The unit of measurement of rock permeability, i.e. the extent to which it will allow a fluid to flow through it.
The permeability of most oil and gas reservoir rocks is measured in millidarcies, (thousandths of a Darcy).DECLINE RATE
The rate at which a well's production declines due to natural and sometimes man-introduced forces. Expressed in percent per year. DELINEATION WELL
A name for an appraisal well, usually one drilled specifically to determine the boundary of a discovered reservoir.DEPLETION
Refers to consumption of natural resources which are part of a company's assets. Producing oil, mining, gas and timber companies deal in products that cannot be replenished and, as such, are known as "wasting assets". DEPTH MAP
A relief map of a sub-surface geological structure where the contours relate to depths from the surface datum level. This is a further interpretation of a seismic time map.DERRICK
The tower-like structure that houses most of the hoisting and lowering equipment & drilling controls.DEVELOPMENT PHASE
The phase in which a proven oil or gas field is brought into production by drilling production (development) wells. DEVELOPMENT WELL
Any well drilled in the course of extraction of reservoir hydrocarbons.DEVIATED WELL/HOLE
A well whose path has been deliberately diverted from the vertical. Although relatively costly to drill, they are used particularly offshore to reach distant parts of a reservoir from a single platform. Deviated, or directional drilling up to 60º to 70º from the vertical is now fairly common. Greater deviation is possible with special equipment. DIRECTIONAL DRILLING
The technique of drilling at an angle from the vertical by deflecting the drill bit. Directional wells are drilled to develop an offshore lease from one drilling platform; to reach a pay zone where drilling cannot be done, such as beneath a shipping lane.DISCOVERY WELL
Exploratory well which discovers a new oil/gas field (see WILDCAT). DIFFERENTIAL PRESSURE
The difference between the pressure in a well due to the mud column and the pressure in the surrounding rock at any point. See also Sticking.DIP (DIPMETER)
The inclination from the horizontal of to the surface of a geological structure. A Dip Meter indicates dip relative to a well bore.DIRECTIONAL DRILLING
Controlled drilling at a specified angle from the vertical. DOWN DIP
An area of a structure where the top of the formation is lower than the point under consideration.DOWN HOLE
Down a well. The expression covers any equipment, measurement, etc., in a well or designed for use in one.DOWNTIME
A period when any equipment is unserviceable or out of operation for maintenance etc.DRAWWORKS
Hoisting mechanism on a drilling rig which spools off or takes in the drilling line and thus raises or lowers the drill string and bit.DRILL BIT
The component at the end of the drill string that cuts the rock and makes a hole.DRILL COLLAR
Heavy-walled sections of pipe included at the bottom of the drill string to apply weight to the drill bit during drilling. DRILL CUTTINGS
Chips and small fragments of drilled rock that are brought to the surface by the flow of the drilling mud as it is circulated.DRILL PIPE
Steel pipe, in approximately 30-foot (9-meter) lengths, screwed together to form a continuous pipe extending from the drilling rig to the drilling bit at the bottom of the hole. Rotation of the drill pipe and bit causes the bit to bore through the rock. DRILL STEM TESTS (DST)
Conventional method of testing a formation to determine its potential productivity before installing production casing in a well. A testing tool is attached to the bottom of the drill pipe and placed opposite the formation to be tested which has been isolated by placing packers above and below the formation. Fluids in the formation are allowed to flow up through the drill pipe by establishing an open connection between the formation and the surface. DRILL STRING
String of individual joints of pipe that extends from the bit to the kelly and carries the mud down to, and rotates, the bit. DRILLING FLUIDS
While a mixture of clay and water is the most common drilling fluid, wells can also be drilled with air, nitrogen, natural gas, oil, or plain water as the drilling fluid.DRY HOLE
Generally refers to any well that does not produce oil or gas in commercial quantities. DUAL COMPLETION
Completion of a well in which two separate formations may be produced at the same time. Production from each zone is segregated by running two tubing strings with packers, or running one tubing string with a packer and producing the other zone through the annulus. DRY GAS
Natural gas composed mainly of methane with only minor amounts of ethane, propane and butane and little or no heavier hydrocarbons in the gasoline range.