Oil&Gas Dictionary_1

Oil & Gas Dictionary_1 

A

Abandoned
A dry hole in which no producible oil or gas was present, or a well that has stopped producing. Abandoned wells must be plugged to prevent seepage of oil, gas, or water from one formation to another.

Active well
A well in mechanical condition for production or service use (i.e., in active production or service use).

Anticline
An upfold or arch of stratified rock in which the beds or layers bend downward in opposite directions form the crest or axis of the fold.

API
The American Petroleum Institute is the oil industry’s trade organization. API’s research and engineering work provides a basis for establishing operating and safety standard issues; specifications for the manufacturing of oil field equipment; and furnishes statistical and other information to related agencies.

Associated gas
Gas combined with oil. Known also as gas cap gas and solution gas, it provides the drive mechanism needed to force oil to the surface of a well. Associated gas is normally present in an oil reservoir in the early stages of production.

B

Barrel
The standard unit of measure of liquids in the petroleum industry; it contains 42 U.S. standard gallons.

Barrel of Oil Equivalent (BOE)
The amount of energy resource (in this document, natural gas) that is equal to one barrel of oil on an energy basis. The conversion is based on the assumption that one barrel of oil produces the same amount of energy when burned as 5,620 cubic feet of natural gas.

Basin
A depression of the earth’s surface into which sediments are deposited, usually characterized by sediment accumulation over a long interval; a broad area of the earth beneath which layers of rock are inclined, usually from the sides toward the center.

Bed
A layer of rock, usually sediments, which is homogeneous (the same) in composition. One bed is separated from another by a bedding plane.

Bid
An offer for an OCS lease submitted by a potential lessee in the form of a cash bonus dollar amount or other commitments as specified in the final notice of sale.

Block
A numbered area on an OCS leasing map or official protraction diagram (OPD). Blocks are portions of OCS leasing maps and OPD’s that are themselves portions of planning areas. Blocks vary in size, but typical ones are 5,000 to 5,760 acres (about 9 square miles or 2,304 hectares). Each block has a specific identifying number, area, and latitude and longitude coordinates that can be pinpointed on a leasing map of OPD.

Blowout
An uncontrolled flow of gas, oil, or other fluids from a well to the atmosphere. A well may blow out when formation pressure exceeds the pressure overburden of a column of drilling fluid.

Blowout preventer

A special assembly of heavy-duty valves, commonly called the BOP stack, installed on top of a well which can be closed to prevent high-pressure oil or gas from escaping (a blowout) from the well hole during drilling operations.

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.

Borehole
The hole in the earth made by the drill; the uncased drill hole from the surface to the bottom of the well.

C

Casing
Steel pipe used in oil wells to seal off fluids in the rocks from the bore hole and to prevent the walls of the hole from caving.

Casinghead
The top of the casing set in a well; the part of the casing that protrudes above the surface and to which the control valves and flow pipes are attached.

Casinghead gas
Gas produced from an oil well as distinguished from gas from a gas well. The casinghead gas is taken off at the top of the well or at the separator.

Choke
A type of orifice installed at the surface on the tubing string to adjust and control the amount of oil or gas flowing from a well. It is customary to refer to the production of a well as so many barrels or thousands of cubic feet through a 1/4-inch or 1/2-inch choke, or whatever the size of the opening. The flowing pressure exerted by the well’s production give an indication of the strength of the well, and is helpful in determining whether a well is commercial.

Commercial well
A well of sufficient net production that it could be expected to pay out in a reasonable time and yield a profit from the operation. A shallow 50-barrel-a-day well in a readily accessible location onshore could be a commercial well. Such a well in virtually any offshore area where enormously expensive producing facilities and pipe lines would have to be constructed would not be considered commercial.

Completed well
A well that has been mechanically completed for production or service use. There may be more than one completed zone in the well. (See Active well.)

Concession
Usually used in foreign operations and refers to a large block of acreage granted to the operator by the host government for a certain time and under certain government conditions which allows the operator to conduct exploratory and/or development operations. The Concession Agreement assures the holder of certain rights under the law.

Condensate
A natural gas liquid with a low vapor pressure, compared with natural gasoline and liquified petroleum gas. It is produced from a deep well where the temperature and pressure are high. Gas condenses as it rises up the wellbore and reaches the surface as condensate. Similarly, condensate separates out naturally in pipelines or in a separation plant by the normal process of condensation.

Condensate
Liquid hydrocarbons produced with natural gas which are separated from it by cooling, expansion, and various other means (also called "distillate”).

Continental margin
A zone separating the emergent continents from the deep sea bottoms.

Continental shelf
A broad, gently sloping, shallow feature extending from the shore to the continental slope.

Continental slope
A relatively steep, narrow feature paralleling the continental shelf; the region in which the steepest descent of the ocean bottom occurs.

COST
Continental Offshore Stratigraphic Test. These tests under the direction of the Minerals Management Service are wells deliberately drilled to provide geological information pertinent to competitive bidding for offshore tracts.