| AC |
alternating
current |
| accelerator |
a
chemical additive that reduces the setting time of cement. See cement and cementing materials. |
| accumulate |
to amass
or collect. When oil and gas migrate into porous formations, the quantity collected is
called an accumulation. |
| accumulator |
a vessel
or tank that receives and temporarily stores a liquid used in a continuous process in a
gas plant. See drip accumulator. On a drilling rig, the storage device for
nitrogen-pressurized hydraulic fluid, which is used in closing the blowout preventers.
See blowout
preventer control unit. |
| acetic acid |
an
organic acid compound sometimes used to acidize oilwells. It is not as corrosive as
other acids used in well treatments. Its formula is C2H4O2, or CH3COOH. |
| acetylene welding |
a method
of joining steel components in which acetylene gas and oxygen are mixed in a torch to
attain the high temperatures necessary for welding. |
| acid |
any
chemical compound, one element of which is hydrogen, that dissociates in solution to
produce free hydrogen ions. |
| acid brittleness |
low
ductility of a metal due to its absorption of hydrogen gas. Also called hydrogen
embrittlement. |
| acid fracture |
to part
or open fractures in productive, hard limestone formations by using a combination of oil
and acid or water and acid under high pressure. See formation fracturing. |
| acid gas |
a gas
that forms an acid when mixed with water. In petroleum production and processing,
the most common acid gases are hydrogen sulfide and carbon dioxide. They both cause
corrosion, and hydrogen sulfide is very poisonous. See sour gas, sour corrosion. |
| acidity |
the
quality of being acid. Relative acid strength of a liquid is measured by pH. A
liquid with a pH below 7 is acid. See pH
value. |
| acidize |
to treat
oil-bearing limestone or other formations with acid for the purpose of increasing
production. Hydrochloric or other acid is injected into the formation under
pressure. The acid etches the rock, enlarging the pore spaces and passages through
which the reservoir fluids flow. The acid is held under pressure for a period of
time and then pumped out, after which the well is swabbed and put back into production.
Chemical inhibitors combined with the acid prevent corrosion of the pipe. |
| acid stimulation |
a well
stimulation method using acid. See acidize. |
| acid treatment |
a method
by which petroleum bearing limestone or other formations are put into contact with an acid
to enlarge the pore spaces and passages through which the reservoir fluids flow. |
| acoustic log |
a record
of the measurement of porosity done by comparing depth to the time it takes for a sonic
impulse to travel through a given length of formation. The rate of travel of the
sound wave through a rock depends on the composition of the formation and the fluids it
contains. Because the type of formation can be ascertained by other logs, and
because sonic transit time varies with relative amounts of rock and fluid, porosity can
usually be determined in this way. |
| acoustic position
references |
a system
consisting of a beacon positioned on the seafloor to transmit an acoustic signal, a set of
three or four hydrophones mounted on the hull of a floating offshore drilling vessel to
receive the signal, and a position display unit to track the relative positions of the rig
and the drill site. Monitoring of the display unit aids in accurate position of the
rig over the site. |
| acoustic signatures |
the
characteristic patterns for various degrees of cement bonding between the casing and the
borehole that appear on an oscilloscope display when a sonic cement bond log is made. |
| acoustic survey |
a
well-logging method in which sound impulses are generated and transmitted into the
formations opposite the wellbore. The time it takes for the sound impulses to travel
through the rock is measured and recorded. Subsequent interpretation of the record
(log) permits an estimation of the rock's porosity and fluid content to be made. The
process is also called sonic logging. See sonic
logging. |
| acoustic well logging |
the
process of recording the acoustic characteristics of subsurface formations, based on the
time required for a sound wave to travel a specific distance through rock. The rate
of travel of the sound wave depends on the composition of the formation, its porosity, and
its fluid content. |
| acre-foot |
a unit
of volume often used in oil reservoir analysis, equivalent to the volume (as of oil or
water) necessary to cover 1 acre to a depth of 1 foot. |
| across |
over.
The term usually relates conditions of fluid flow on one side of a piece of
equipment to conditions on the opposite side (e.g., a pressure drop across a separator). |
| ACT |
automatic
custody transfer |
| activated charcoal |
a form
of carbon characterized by a high absorptive and adsorptive capacity for gases, vapors,
and colloidal solids. |
| adapter |
a device
to provide connection between two other parts. |
| adsorption |
the
accumulation of a thin layer of molecules of gas or liquid on a solid surface. |
| Air/Gas Lift |
lifting
of liquids by injection, directly into the well, of air or gas. |
| allowable |
the
amount of oil or gas that a well is permitted by State authorities to produce during a
given period |
| annular space |
1. the
space surrounding a cylindrical object within a cylinder. 2. the space around a pipe in a wellbore, the outer wall of which may be the wall
of either the borehole or the casing; sometimes termed the annulus. |
| annulus |
also
called annular space. See annular space. |
| anomaly |
a
deviation from the norm. In geology, the term indicates an abnormality such as a
fault or dome in a sedimentary bed. |
| anticlinal trap |
a
hydrocarbon trap in which petroleum accumulates in the top of an anticline. See anticline. |
| anticline |
an
arched, inverted-trough configuration of folded and stratified rock layers. |
| appraisal well |
a well
drilled to further confirm and evaluate the presence of hydrocarbons in a reservoir that
has been found by a wildcat well. |
| API |
American
Petroleum Institute. Headquarters: 1801 K Street, N.W., Washington, D.C. 20006. Division
of Production: 300 Corrigan Tower, Dallas, Texas 75201. |
| API Gravity |
a system
for measuring density of a liquid to be tested which has been adopted as a standard by
API. |
| apron ring |
the
first or lowest ring of plates in a tank. |
| arctic submersible rig |
a mobile
submersible drilling structure used in arctic areas. The rig is moved onto the
drilling site and submerged during periods when the water is free of ice. All
equipment below the waterline is surrounded by a caisson to protect it from damage by
moving ice. The drilling deck has no square corners so that moving ice can better
flow around it. |
| artificial lift |
any
method used to raise oil to the surface through a well after reservoir pressure has has
declined to the point at which the well no longer produces by means of natural energy.
Sucker rod pumps, gas lift, hydraulic pumps, and submersible electric pumps are the
most common forms of artificial lift. |
| associated gas |
natural
gas, commonly known as gas-cap gas, which overlies and is in contact with crude oil in the
reservoir. |
