| gaging nipple |
a small section of pipe in the top of a tank
through which a tank may be gaged. |
| galena |
lead sulfide (PbS). Technical grades
(specific gravity about 7) are used for increasing the density of drilling fluids to
points impractical or impossible with barite. |
| gall |
damage to steel surfaces caused by friction
and improper lubrication. |
| galvanic
corrosion |
a type of corrosion that occurs when a small
electric current flows from one piece of metal equipment to another. It is
particularly prevalent when two dissimilar metals are present in an environment in which
electricity can flow (as two dissimilar joints of tubing in an oil or gas well). |
| gas |
a compressible fluid that fills any container
in which it is confined. Technically, a gas will not condense when it is compressed
and cooled, because a gas can exist only above the critical temperature for its particular
composition. Below the critical temperature, this form of matter is known as a
vapor, because liquid can exist and condensation can occur. Sometimes the terms
"gas" and"vapor" are used interchangeably. The latter, however, should
be used for those streams in which condensation can occur and that originate form, or are
in equilibrium with, a liquid phase. |
| gas anchor |
a tubular, perforated device attached to the
bottom of sucker-rod pump that helps to prevent gas lock. The device works on the
principle that gas, being lighter than oil, rises. As well fluids enter the anchor,
the gas breaks out of the fluid and exits from the anchor through perforations near the
top. The remaining fluids enter the pump through a mosquito bill (a tube with the anchor),
which has an opening near the bottom. In this way, all or most of the gas escapes
before the fluids enter the pump. |
| gas cap |
a free-gas phase overlying an oil zone and
occurring within the same producing formation as the oil. |
| gas cutting |
a process in which gas becomes entrained in a
liquid. |
| gas drive |
the use of the energy that raises from the
expansion of compressed gas in a reservoir to move crude oil to a wellbore. Also
call reservoir drive mechanism. |
| gas input well |
a well into which gas in injected for the
purpose of maintaining or supplementing pressure in an oil reservoir. More commonly
called a gas injection well. |
| gas lift |
the process of raising or lifting fluid from a
well by injecting gas down the well through tubing or through the tubing-casing annulus.
Injected gas aerates the fluid to make it exert less pressure than the formation
does; consequently, the higher formation pressure forces the fluid out of the
wellbore. Gas may be injected continuously or intermittently, depending on the
producing characteristics of the well and the arrangement of the gas-lift equipment. |
| gas lift valve |
a device installed on a gas lift mandrel,
which in turn is put on the tubing string of a gas lift well. Tubing and casing
pressures cause the valve to open and close, thus allowing gas to be injected into the
fluid in the tubing to cause the fluid to rise to the surface. |
| gas lock |
1. a condition sometimes encountered in a
pumping well when dissolved gas, released from solution during the upstroke of the
plunger, appears as free gas between the valves. If the gas pressure is sufficient,
the standing valve is locked shut, and no fluid enter the tubing. 2. a device fitted to the gauging hatch on a pressure tank that
enables manual dipping and sampling without loss of vapor. |
| gas plant
products |
natural gas liquids recovered from natural gas
in gas processing plant and, in some situations, from field facilities. |
| gas processing
plant |
a facility designed: (1) to achieve the recovery of natural gas liquids from the stream
of natural gas which may or may not have been processed through lease separators and field
facilities, and
(2) to control the quality of the natural gas to be
marketed. |
| gas sand |
a stratum of sand or porous sandstone from
which natural gas is obtained. |
| gas well |
a well that primarily produces gas.
Legal definitions vary among the states. |
| gas-cut mud |
a drilling mud that contains entrained
formation gas, giving the mud a characteristically fluffy texture. Then entrained
gas in 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 reduce the chance of a kick. |
| gas-cutting |
a process in which gas becomes entrained in a
liquid. |
| gas-oil ratio |
a measure of the volume of gas produced with
oil, expressed in cubic feet per barrel of cubic meters per tonne. |
| gasing-up |
injection of nitrogen for gas lift valving. |
| gasket |
any material (i.e., paper, cork, asbestos, or
rubber) used to seal two essentially stationary surfaces. |
| gate valve |
a valve that employs a sliding gate to open or
close the passage in it. |
| gathering lines |
the flow lines which run from several wells to
a single tank battery. |
| gauge joint |
the heaviest-wall casing section of the
string, usually located just below the preventers or tree. |
| gauge ring |
a cylindrical metal ring used to guide, and
centralize, packers or tools inside casing. |
| gauge trip |
running of a gauge on tubing or slickline to
verify casing dimensions. |
| gel |
a semisolid, jelly-like state assumed by some
colloidal dispersions at rest. When agitated, the gel converts to a fluid state.
Also a nickname for bentonite. |
| gel strength |
a measure of the ability of a colloidal
dispersion to develop and retain a gel form, based on its resistance to shear. The
gel, or shear, strength of a drilling mud determines its ability to hold solids in
suspension. Sometimes bentonite and other colloidal clays are added to drilling
fluid to increase its gel strength. |
| general gas law |
any law relating to the pressure, temperature,
or volume of a gas. |
| geologist |
a scientist who gathers and interprets data
pertaining to the rocks of the earth's crust. |
| geology |
the science of the physical history of the
earth and its life, especially as recorded in the rocks of the crust. |
| get a bite |
to set tools in casings. |
| gin-pole truck |
a truck equipped with a pair of poles, and
hoisting equipment for use in lifting heavy machinery around a lease. |
| girth or girt |
one of the horizontal braces between the legs
of a derrick. |
| gone to water |
describes a well in which water production is
increasing. |
| gland |
a device used to form a seal around a
reciprocating or rotating rod (as in a pump) to prevent fluid leakage. Specifically,
the movable part of a stuffing box by which the packing is compressed. |
| glass disk |
a sub with a glass blockage in the bore, used
to isolate a surge chamber in gravel packing or perforation cleaning operations. |
| GLR |
gas-liquid-ratio |
| go in the hole |
to lower the drill stem, tubing, casing, or
sucker rods in to the wellbore. |
| go-devil |
1. a device that is inserted into a pipeline
for the purpose of cleaning; a line scraper. Also called a pig. 2. a device that is lowered into the borehole of a well for various
purposes such as enclosing surveying instruments, detonating instruments, and the like. |
| gooseneck |
the curved connection between the rotary hose
and the swivel. |
| GPG |
grains per gallon |
| GRN |
gamma-ray-neutron (a well log). |
| gradient |
pressure drop |
| grapple |
a mechanism that is fitted into an overshot to
grasp and retrieve fish from the borehole. The interior of a grapple is wickered to
engage the fish. |
| grass gooser |
a hoe or other kind of weed cutter. |
| grave-pack |
to place a slotted or perforated liner in a
well and surround it with gravel |
| gravel pack |
a mass of very fine gravel placed around a
slotted liner in a well. |
| gravel packing |
a method of well completion in which a slotted
or perforated liner, often wire-wrapped, is placed in the well and surrounded by gravel.
If open hole, the well is sometimes enlarged by underreaming at the point where the
gravel is packed. The mass of gravel excludes sand from the wellbore but allows
continued production. |
| gravel-pack
packer |
a packer used for the well completion method
of gravel packing. |
| gravitometer |
a device for measuring and recording the
specific gravity of a gas or liquid passing a point of measurement. |
| gravity - API |
The specific gravity or density of oil
expressed in terms of a scale devised by the American Petroleum Institute. The
lighter the oil, the greater the gravity; other factors being equal, the higher the API
gravity, the better price the oil will bring. |
| gravity -
specific |
density expressed as the ratio of the weight
of a volume of substance to the weight of an equal volume of another standard substance.
In the case of liquids and solids, the standard is water. In the case of
natural gas or other gas materials, the standard is air. |
| gravity drainage |
the movement of fluids in a reservoir
resulting from the force of gravity. In the absence of an effective water or gas
drive, gravity drainage is an important source of energy to produce oil, and it may also
supplement other types of natural drive. Also called segregation drive. |
| gravity survey |
an exploration method in which an instrument
that measures the intensity of the earth's gravity is passed over the surface or through
the water. In places where the instrument detects stronger or weaker than normal
gravity forces, a geologic structure containing hydrocarbons may exist. |
| Gray valve |
see inside
blowout preventer. |
| grease injector |
a surface device used in pressure control for
slickline. |
| greasing out |
when water-insoluble greasy materials (e.g.,
emulsifiers, lubricants) separate out of drilling fluids. |
| grind out |
see shake
out |
| gross production |
the total production of oil from a well or
lease during a specified period of time. |
| guar gum |
a naturally occurring hydrophilic
polysaccharide derived from the seed of the guar plant. The gum is chemically
classified as a galactomannan. Guar gum slurries made up in clear fresh or brine
water possess pseudoplastic flow properties. |
| guide ring |
a cylindrical metal ring used to guide packers
past casing obtrusions. |
| guide shoe |
1. 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 center of the shoe allow drilling
fluid to pass up into the casing while it is being lowered and allows cement to pass out
during cementing operations. Also called casing
shoe. 2. a device, similar to a
casing shoe, placed at the end of other tubular goods. |
| gum |
any hydrophilic plant polysaccharides or their
derivatives that, when dispersed in water, swell to produce a viscous dispersion or
solution. Unlike resins, they are soluble in water and insoluble in alcohol. |
| gumbo |
any relatively sticky formation (such as clay)
encountered in drilling |
| gun-perforate |
to create holes in casing and cement set
through a productive formation. A common method of completing a well is to set
casing through the oil-bearing formation and cement it. A perforating gun is then
lowered into the hole and fired to detonate high-powered jets or shoot steel projectiles
(bullets) through the casing and cement and into the pay zone. The formation fluids
flow out of the reservoir through the perforations and into the wellbore. See perforating gun. |
| gun the pits |
to agitate the drilling fluid in a pit by
means of a mud gun, electric mixer, or agitator. |
| gunk plug |
a slurry in crude or diesel oil containing any
of the following materials or combinations: bentonite, cement, attapulgite, and guar
gum (never with cement). Used primarily in combating lost circulation. |
| gunk slurry |
a slang term to denote a mixture of diesel oil
and bentonite. |
| gunk squeeze |
a bentonite and diesel oil mixture that is
pumped down the drill pipe and into the annulus to mix with drilling mud. The stiff,
putty-like material is squeezed into lost circulation zones to seal them. |
| gusher |
an oilwell 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. |
| guy line |
a wireline attached to a mast, derrick, or
offshore platform to stabilize it. See wind
guy line. |
| guy line anchor |
a buried weight or anchor to which a guy line
is attached. See deadman. |
| guy wire |
a rope or cable used to steady a mast or pole. |
| guyed-tower
platform rig |
a compliant offshore drilling platform used to
drill development wells. The foundation of the platform is a relatively lightweight jacket
upon which all equipment is placed. A system of guy wires anchored by clump weights
helps secure the jacket to the seafloor and allows it to move with wind and wave
forces. See platform rig. |
| gyp |
(slang) gypsum |
| gypsum |
a naturally occurring crystalline form of
calcium sulfate in which each molecule of calcium sulfate is combined with two molecules
of water. See calcium sulfate. |
