Oil & Gas Dictionary_1
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.
A well in mechanical condition for production or service use (i.e., in active
production or service use).
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.
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.
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.
The standard unit of measure of liquids in the petroleum industry; it contains
42 U.S. standard gallons.
Barrel of Oil Equivalent
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.
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.
A layer of rock, usually sediments, which is homogeneous (the same) in
composition. One bed is separated from another by a bedding plane.
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
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.
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.
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
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.
The hole in the earth made by the drill; the uncased drill hole from the
surface to the bottom of the well.
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.
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.
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.
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.
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.
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.)
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.
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
Liquid hydrocarbons produced with natural gas which are separated from it by
cooling, expansion, and various other means (also called "distillate”).
A zone separating the emergent continents from the deep sea bottoms.
A broad, gently sloping, shallow feature extending from the shore to the
A relatively steep, narrow feature paralleling the continental shelf; the
region in which the steepest descent of the ocean bottom occurs.
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.