Technical Thesaurus oil & gas
Letter
Gales
10 minute sustained winds of
greater than 33 knots (Beaufort force 8 or greater).
Gall
To damage or destroy a finished
metal surface, as a shaft journal by moving contact with a bearing without sufficient
lubrication. To chafe by friction and heat as two pieces of metal are forcibly
rubbed together in the absence of lubrication.
Gamma-ray logging
Strip recording of the intensity
of natural radio-activity versus depth, obtained when a suitable detector is
lowered through a bore hole.
Gas anchor
A device for the bottom hole
separation of oil and gas in a pumping well. The gas anchor (a length of tubing
about five feet long) is inside a larger pipe with perforations at the upper
end. Oil in the annulus between the well's casing and tubing enters through the
perforations and is picked up by the pump; the gas goes out through the casing
and is disposed of via the wef
Gas cap
A layer of natural gas above the
oil in an oil reservoir.
Gas cap drive
A recovery mechanism whereby the
oil from the reservoir is displaced by the downward expansion of an overlying
gas cap.
Gas field
A field containing natural gas but
no oil.
Gas fuel
Gas consumed by the different
facilities on platforms and onshore plant for operation of equipment such as
power supply. heating etc.
Gas grid
A network of pipelines used to
distribute gas to industrial and domestic consumers.
Gas injection
The process whereby separated
associated gas is pumped back into a reservoir for conservation purposes or to
maintain the reservoir pressure.
Gas natural
It is the portion of petroleum
that exists in the gaseous phase or is in solution in crude oil in natural
underground reservoirs, and which is gaseous at atmospheric conditions of pressure
and temperature. Natural gas may include amounts of non-hydrocarbons such as
hydrogen sulphide, nitrogen, oxygen and/or carbon dioxide.
Gas oil
The medium distillates from the
oil refining process intermediate between light lubricating oils and kerosene;
used to produce diesel fuel and burned in central heating systems.
Gas pipeline
A pipeline used to transport gas
between two places either offshore or onshore.
Gas raw
It is a mixture of hydrocarbons
and non-hydrocarbons which exist as a gas in an underground reservoir. It is
the complete well stream and includes LPG and condensate. Its volume is
reported at Standard Conditions.
Gas sand
A stratum of sand or porous
sandstone from which natural gas is obtained.
Gas show
The gas that appears in drilling
fluid returns, indicating the presence of a gas zone.
Gas sour
Gas that contains hydrogen
sulphide (H2S).
Gas sweep
Amount of gas required to prevent
build-up of liquid volumes in gas transport lines.
Gas sweet
Hydrocarbon gas free from sulphur
compounds.
Gas to oil ratio
This is the proportion of
associated gas produced with the oil and is usually expressed in standard cubic
feet or gas per barrel of oil (SCF/BBL). The higher the ratio the more
separation facilities are required so that the gas can be transported to shore
separately, flared or reinjected into the reservoir.
Gas-cut mud
A drilling mud that has 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 lessen the chance of a
blowout.
Gaseous fuels
The light, highly volatile
distillates from the refining process; used to manufacture motor spirit,
aviation gasoline and camping gas.
Gasification
The process whereby gaseous fuel
is manufactured from a solid to liquid fuel.
Gasoline
See motor spirit.
Gauge (tide)
A device for measuring the height
of tide. A graduated staff in a sheltered area where visual observations can be
made; or it may consist of an elaborate recording instrument making a
continuous graphic record of tide height against time. Such an instrument is
usually actuated by afloat in a pipe communicating with the sea through a small
hole which filters out shorter waves.
Gauging
The process of measuring bulk
quantities of liquid. The various steps in the process involve accurate
measurement of volume. temperature, specific gravity or density, and finally a
calculation of the volume at a standard temperature.
Gel
See bentonite.
General bathymetric chart of the oceans (GEBCO)
A global series of small scale
bathymetric charts. Edited through international cooperation by IHO and IOC.
Geodesic line
The shortest line on a
mathematically derived surface, between two points on that surface. A geodesic
line on a reference spheroid is called a geodetic line. Also termed as
geodesic.
Geodesy
Science of the geometrical
measurement of the Earth; in survey it is concerned with reference for
horizontal and vertical datums for latitude/longitude/height/depth, charting
(datum) and relationships between different datums, map projections (such as
UTM).
Geographic information system
A management system for the
unified view of geographical data.
Geographical coordinates (geogs)
Position expressed as
latitude/longitude in degrees, minutes and seconds (as against grid
coordinates).
Geologist
A scientist who gathers and
interprets data pertaining to the strata of the Earth's crust.
Geolograph
A device of a drilling rig to
record the drilling rate or rate of penetration during each tour.
Geology
The science relating to the
history and development of the Earth's crust.
Geophones
The detectors used in seismic
surveys to pick up sound waves reflected from sub-surface strata.
Geophysical
Concerning the sea-bed and below,
divided into Shallow: of interest for foundations, pipelaying and initial
drilling conditions (e.g. analogue positioning data) Deep: of interest for
hydrocarbon reserve.
Geophysics
The physics of the Earth: a
hybrids discipline involving a combination of physical and geological
principles.
Geosyncline
A large sedimentary basin in which
extremely deep layers of sediments have accumulated over a long period of time.
Geotechnical
Relating to engineering study of
subsurface soils; involves specialised drilling and/or sampling for soil
analysis and testing; relevant to rig leg penetration or offshore piping among
others
Geothermal gradient
A measure of the rise of rock
temperature with increasing depth below the Earth's Face.
Gland
A sleeve which compresses the
packing around a shaft or piston.
Global positioning system (GPS)
A satellite navigation system
intended to provide highly accurate position and velocity information in three
dimensions and precise time and time interval on a global basis continuously.
Go-devil
A type of pig with self-adjusting
blades used to clear the interior of pipelines.
Going in hole
Lowering the drill string into the
well bore.
Gooseneck
A nipple in the shape of an
inverted U attached to the top of the swivel (q.v.) and to which the mud hose
is attached.
GOR
See gas to oil ratio.
Grabsampler
Soil sampling device lowered to
sea-bed and, using spring loaded jaws to penetrate, produces samples up to
Grad (or grade)
A unit of angle measurement, equal
to the angle at the centre of a circle, subtended by one four hundredth part of
its circumference.
Graveyard tour
Shift of duty on a drilling rig
that starts at or about midnight. Compare daylight tour and evening tour.
Gravimetric survey
A geological survey method in
which measurements of the variations in the surface gravitational field are
used to determine the nature of the underlying rocks.
Gravity
The attraction exerted by the
Earth's mass on objects at its surface; the weight of a body. See API gravity
and specific gravity.
Gravity platform
A platform, generally made of
reinforced concrete, which sits on the sea- bed and is kept in position by its
own weight, no piling being used.
Greenwich Mean Time (GMT)
See time and universal time.
Grid
1. The cartesian coordinate system
used in projections such as UTM, Lambert, Stereographic. 2. The layout of
survey lines in a survey programme, usually parallel lines at a set interval with
perpendicular cross lines.
Grid coordinates (grid)
Position expressed as
easting/northing in metres/feet (as against geographical coordinates).
Grid -universal transverse
mercator (UTM)
A grid system in which a grid
network is applied to universal transverse mercator projections of zones of the
Earth's surface extending to 80 degrees N. and S. latitudes.
Grief stem
Kelly joint, the top joint of the
rotary drill string that works through the square hole in the rotary table. As
the rotary table is turned by the drilling engines, the grief stem and the
drillpipe are rotated. Grief stems are heavy, thick-walled tubular pieces with
squared shoulders that are made to fit into the hole in the rotary table.
Gross liquid
Total amount of liquid (oil, condensate
and water) produced via a well from a reservoir.
Gross tonnage
The volume of the interior of a
crude oil tanker including all spaces which, are permanently closed in (but
excluding the double bottom). Expressed in tons per
Guide shoe
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 centre
of the shoe allows drilling fluid to pass up to the casing while it is being
lowered and cement to pass out during cementing operations. Also called casing
shoe.
Gumbo
A heavy, sticky mud formed
downhole by certain shales when they become wet from the drilling fluid.
Gun perforator
A device fitted with a vertical
series of explosive charges that is lowered down a well on a wire line to
perforate the formation; also known as a perforating gun.
Gusher
An oil well 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.
Gyroscope
A rapidly rotating mass free to
move about one or both axes perpendicular to the axis of rotation and to each
other. It is characterised by gyroscopic inertia and precession. Sometimes
shortened to gyro.
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