Technical
Thesaurus oil & gas
G
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
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.