Technical Thesaurus oil & gas
Letter
Daily peak
The
maximum volume of gas delivered in anyone day during a given period, usually a
calendar year.
Dangerous area
Definition
of an area so far as danger may arise from electrical causes.
Dangerous atmosphere
An
atmosphere containing any flammable gases or vapour in a concentration capable
of ignition by any cause. or containing a toxic gas or vapour in such a
concentration which will be dangerous to human life.
Darcy
A
unit of permeability. A porous medium has a permeability of I darcy when a
pressure gradient of I atm/cm on a rock sample of 1 cm2 cross section will
force a liquid of 1-cp viscosity through the sample at the rate of I cc per
sec.
Data
General
term used to denote facts. numbers. letters, and symbols. The basic elements of
information; usually but not always expressed in numerical form.
Data bank
A
system for describing. storing, and retrieving high volumes of complex
structured data. A data bank is comprised of the data base and a set of data
bank software (data base management system. DBMS) which store and retrieve
information according to predefined data descriptions. and for carrying out
additional operations. Also called data base system.
Data base
Physical
storage of data belonging to a data bank.
Data processing
Any
operation carried out with data.
Data set
A
logical entity of data consisting of several elements (fields) grouped under
one criterion.
Datum
Any
numerical or geometrical quantity or set of such quantities which may serve as
a reference or base for other quantities. In geodesy two types of datums must
be considered: a horizontal datum which forms the basis for computations of
horizontal control surveys in which the curvature of the earth is considered,
and a vertical datum to which elevations are referred. World Geodetic System
1972 (WGS72). Represents pre 1972 data evaluation of the best global fit datum.
Used for Transit and early GPS. World Geodetic System 1984 (WGS84). Represents
pre 1984 data evaluation of the best global fit datum. Used for transit and
LPS. Mean Sea Level (MSL). The average height of the surface of the sea at a
tide station for all stages of the tide over a given period,usually determined
from hourly height readings measured from a fixed predetermined reference level
(ChartDatum). Lowest Astronomical Tide (LAT). The lowest tide level which can
be predicted to occur under average meteorological conditions and under any
combination of astronomical conditions.
Datum (tidal)
A level
of the sea defined by some phase of the tide, from which water depths and
heights of tide are reckoned.
Datum chart
A
permanently established surface from which soundings or tide heights are
referenced, usually low water. Also called datum, datum level, datum plane,
hydrographic datum, reference level, reference plan. See datum (tidal).
Datum(geodetic)
A
reference surface consisting of five quantities: the latitude and longitude of
an initial point, the azimuth of a line from this point, and the parameters of
the reference spheroid. It forms the basis for the computation of horizontal
control surveys in which the curvature of the Earth is considered. See
horizontal control datum.
Datum(sounding)
The
horizontal plane or tidal datum to which the soundings on a hydrographic survey
are reduced. Also called datum for sounding reduction.
Daylight tour
The
shift of duty on a drilling rig that starts at or about daylight; also called
morning tour. See evening tour and graveyard tour.
Dead freight
Freight
rate which is paid on empty space in the vessel when the, charterer is
responsible for the freight rate of a full cargo. It should be paid before
sailing.
Dead oil
Crude
oil containing no dissolved gas. Compare live oil.
Dead well
A
well that will not flow, and in order to produce must be kicked off or put on
artificial lift.
Deadline
Refers
to the end of the hoisting line which is not reeled on the hoisting drum of the
rig. This end of the line is usually anchored to the derrick or mast
substructure and does not move as the travelling block is hoisted, hence the
term deadline. Compare fast line.
Deadline
tie-down anchor
A
device to which the deadline is attached, securely fastened to the mast or derrick
substructure. Also called a deadline anchor.
Deadman
Deadman control
A
device for shutting down an operation should the attendant or operator become
incapacitated. The attendant using such a device must consciously exert pressure
on a hold-down handle or lever to work the job. When pressure is relaxed owing
to some emergency, the operation will automatically come to a halt.
Deadweight tonnage (D.W.T.)
This
is the actual number of tons of cargo, bunkers, stores, etc., that can be put
on board a ship to bring her down to her marks.
Deadweight tons
Total
carrying capacity of a ship in tons when loaded to appropriate freeboard during
the summer season.
Deadwood
Material
inside a tank or other vessel such as pipes, supports, and construction members
that reduce the true volume of the tank.
Deaerator
A
piece of equipment designed to remove dissolved oxygen and carbon dioxide from
boiler fed water in order to reduce corrosion in the boiler system.
Debt
A sum
of money owed by one person or organisation to another and repayable within a
fixed period of time.
Decantation
Separation
of a solid from a liquid, or a liquid from a solid, by sucking, pumping or
pouring the liquid away without disturbing the solid or liquid which has
settled below.
Decomposition
The
breaking up of a chemical compound to form two or more simpler molecules.
Decompression chamber
A
special chamber in which a diver gradually returns to normal conditions after
working at high pressure underwater.
Defoamer or defoaming agent
Any
substance used to prevent, reduce or eliminate foam by reducing the surface
tension.
Degasser
The
equipment used to remove unwanted gas from a liquid, especially from drilling
fluid.
Degassing drilling mud
An
important part of well-drilling operations is keeping the drilling mud free of
entrained gas, bubbles that enter the mud as it circulates downhole through
gaseous formations. One of three functions of mud is to provide sufficient
hydrostatic head to control a kick when high pressure oil or gas is
encountered. When mud of a certain density is circulated, it can become infused
with gas to an extent that, although the volume of mud may increase, the
density is severely reduced. To guard against this dangerous situation, the mud
is degassed at the surface. Several kinds of equipment get the gas out, but all
have one aim in common; to make it possible for the gas bubbles to free
themselves. One method flows the mud over wide sheets so the slurry is no more
than one-eighth to three-eighths thick so the bubbles may come to the surface
and escape. Another method sprays the mud against a baffle in a spray tank that
squeezes out the gas. A third method directs the mud through a vacuum tank
where, under reduced atmospheric pressure, the bubbles of gas expand and break
out of the slurry.
Degree day
A
measure of the extent to which the mean daily temperature falls below an
assumed base, say
Dehydration
The
elimination or removal of water which is chemically combined with a substance.
Delocalised electrons
Electrons
that are not associated with a particular atom or bond in a molecule, as in
aromatic compounds such as benzene.
Demobilisation
End
of survey work or other work period, return to port; often involving removal of
hardware equipment or personnel; the contractual time for the project (mobilisation).
Demulsifier
A
chemical used to "break down" crude oil/water emulsions. The chemical
reduces the surface tension of the film of oil surrounding the droplets of
water.
Demurrage
The
sum agreed by charter to be paid as damage for delay beyond the stipulated time
for loading or discharging.
Density
A
physical property of a material defined as the weight of unit volume at a
certain temperature.
Density log
A
well log which records the formation density. The tool consists of a gamma-ray
source and one or more gamma-ray detectors. Gamma-rays are back-scattered from
the formation due to
Density of soundings
Intervals
between lines of sounding and soundings in the same line. Density of soundings
mostly depends on the scale and nature of the survey. Also called frequency of
soundings.
De-oiling
The
removal of oil particles from water in order to produce clean effluent water.
Depletion control
A
restriction imposed on the rate at which oil and gas reserves can be depleted,
i.e. from the reservoir.
Depletion rate
The
rate at which an oil field is exhausted.
Depletion type reservoir
A
reservoir from which the oil (or gas) is produced by expansion of the fluid,
rather than an influx of water or expansion of a gas cap. Oil recovery by
reservoir depletion is low, commonly between five per cent and 20 per cent of
the oil in place. Gas recovery is high, 70-80 per cent
Deployment
Putting
underwater equipment over the stern or side or moon pool of survey ship; start
work; duration may be prescribed by specification.
Depositional environment
The
conditions under which a series of rock strata were laid down. Depositional
environments are divided into five groups: marine (ocean- borne), aeolian
(wind-borne), alluvial (river borne), deltaic (borne by a river at its delta),
and interdeltaic (between river deltas).
Depreciation
The
reduction in the value of plant or equipment over time due to wear, tear and
obsolescence.
Depth ( charted)
The
vertical distance from the chart datum to the bottom.
Depth differences
The
differences in depth which may be encountered in hydrographic surveys at
crossing of cross lines and principal lines of soundings.
Derived fuel (energy)
A
fuel (or form of energy) which is produced from a basic fuel such as coal (e.g.
electricity, coke or town gas).
Derrick
The
elongated pyramid of latticed steel mounted over the bore hole for drilling and
well servicing purposes.
Derrick (production)
A
steel structure built over a production well for raising and lowering
production equipment and to provide space and support for stacking tubing and
hanging sucker rods when out of the hole.
Derrick barges
Large
barges having a crane used for lifting heavy equipment on to or off an offshore
platform.
Derrick floor
A
raised dais at the base of the derrick carrying the drilling table; Sometimes
called the drilling or rig floor.
Derrick man
The
member of the drilling crew who works up the derrick; also known as the derrick
monkey.
Derv / derv fuel
An
acronym for diesel engine road vehicle fuel; a medium-Iight liquid fuel derived
from gas oil.
Desalting
The
removal of inorganic chloride-type impurities from crude oils.
Desanders
See
hydrocyclones.
Desiccation (drying)
The
removal of moisture or the prevention of moisture pick-up from the surrounding
atmosphere.
Desilters
See
hydrocyclones.
Desulphurisation
Process
for the removal of sulphur and its compounds from crude oil or refined
products.
Detergent
A
cleansing liquid or solid.
Deterioration
Any
undesirable chemical or physical change.
Development phase
The
phase in which a proven oil or gas field is brought into production by drilling
production wells.
Development well
A
well drilled with a view to producing oil or gas from a proven field.
Deviated well
A
well drilled in such a way that its controlled direction departs progressively
from the vertical; such wells are drilled in order to reach different parts of
a reservoir from a single platform. A well may also be deviated to avoid junk
drilling equipment left in the original hole.
Deviated well
A
well drilled in such a way that its controlled direction departs progressively
from the vertical; such wells are drilled in order to reach different parts of
a reservoir from a single platform. A well maly also be deviated to avoid
junked drilling equipment left in the original hole.
Deviation
The
inclination of the well bore from the vertical. The angle of deviation, angle
of drift, or drift angle is the angle in degrees that shows the variation from
the vertical as revealed by a deviation survey. See deviation survey.
Deviation (magnet)
The
angle between the compass needle and the magnet meridian, expressed in degrees
east or west of magnetic meridian. Also called deviation.
Deviation drilling
See
directional drilling.
Deviation survey
An
operation made to determine the angle from which a bit has deviated from the
vertical during drilling. There are two basic deviation surveys, or drift
survey, instruments: one reveals the angle of deviation only; the other
indicates both the angle and direction of deviation.
Dew point
The
temperature at which air is saturated with water.
DGPS
Differential
GPS usage mode involving comparison of mobile receiver and stationary reference
receiver, it allows GPS to obtain the high accuracies required for survey. See
differential GPS.
Dialkene
An
aliphatic compound containing two double carbon-to-carbon bonds in its
molecule.
Diamond bit
A
drilling bit that has a steel body surfaced with industrial diamonds. Cutting
is performed by the rotation of the very hard diamonds over the rock surface.
Diesel electric power
The
power supplied to a drilling rig by diesel engines driving electric generators,
used widely offshore and gaining popularity onshore.
Diesel engines
A
high-compression, internal-combustion engine used extensively for powering
drilling rigs. In a diesel engine, air is drawn into the cylinders and
compressed to very high pressures; ignition occurs as fuel is injected into the
compressed and heated air. Combustion takes place within the cylinder above the
piston, and expansion of the combustion products imparts power to the piston.
Diesel fuel
The
light oil fuel that is used in diesel and other compression-ignition engines.
Diesel index
An
index of the ignition quality of diesel fuel obtained by calculation of the
specific gravity and the aniline point of a middle distillate fuel.
Differential GPS
Differential
GPS is implemented by placing a GPS monitor receiver at a precisely known
location. Instead of computing a navigation fix, the monitor determines the
range error to every GPS satellite it can track. These ranging errors are then
transmitted to local users where they are applied as corrections before
computing the navigation result.
Digital
Technique
of representing a sensor's input as numeric data stream (after conversion from
analogue input signal), e.g. all marine seismic including high resolution
relies on multichannel digital techniques (as opposed to analogue).
Digitise
To
convert analogue data (or physical image) to digital data, e.g. echo sounder
data digitised for logging, sonar data digitised for video output.
Dilute
To
reduce the strength of concentration of a solution by the addition of another
liquid.
Diolefin
See
dialkene.
Dip
A
measure of the inclination of rock strata with respect to the horizontal.
Dipping
Measurement
of the depth of liquid in a storage tank by the use of a graduated steel tape
or rod.
Directional drilling
A
technique whereby a well is deliberately deviated from the vertical in order to
reach a particular part of a reservoir. See deviated well, whip stock.
Discovery well
The
first oil or gas well drilled in a new field; the well that reveals the
presence of a petroleum bearing reservoir. Subsequent wells are development
wells. Compare development well.
Dispersant
A
chemical used to reduce the surface tension between two liquids, e.g. break up
an oil slick.
Dispersed phase
The
scattered phase (solid, liquid, or gas) of a dispersion. The particles are
finely divided and completely surrounded by the continuous phase.
Dispersoid
A
colloid or finely divided substance.
Displacement fluids
In
oil well cementing, the fluid, usually drilling mud or salt water, that is
pumped into the well after the cement to force the cement out of the casing and
into the annulus.
Disposal well
A
well used for the disposal of (usually) salt water. The water is pumped into a
subsurface formation sealed off from other formations by impervious strata of
rock; a service well.
Dissolved gas
Gas
contained in solution with the crude oil in the reservoir.
Dissolved gas drive
The
force of expanding gas dissolved in the crude oil in the formation that drives
the oil to the well bore.
Dissolved solids
The
different anions and cations dissolved in formation waters.
Distillates
The
products obtained by condensation during the fractional distillation process,
i.e. the gaseous fuels, kerosene and gas oils.
Distillation
The
process by which liquids are separated or purified by successive vapourisation
and condensation.
Diver
Anyone
who works underwater in a wet suit, diving bell or hyperbaric chamber.
Diverter
An
inflatable torus which, when pressurised, seals off the annulus causing the
drilling mud to be diverted to the mud pits on a drilling platform.
Dividend
The
profit from a company paid to its investors.
Diving bell
A
pressure chamber from which divers work underwater, the water being kept out by
means of high internal air pressure; can also be used as an observation
chamber.
DMT
Acoustic
Dual Mode Transponder made by Sonardyne.
Doghouse
A
smaller shelter located on the rig floor for use by the drilling crew.
Dogleg
An
abrupt change in the direction of a well bore.
Dolomite
A
rock composed of the double carbonate of calcium and magnesium; a common
reservoir material.
Doodlebugger
A
member of a seismic crew.
DOP
Dilution
of Precision. A parameter relating the precision of the position (and/or an
unknown auxiliary) provided by a positioning system to that of the
"observed quantities" directly measured by the system. DOP is a
measure of the influence of the geometry of loci on the precision of position
fixing. OOP is frequently used with a qualifying term such as geometric (GOOP),
horizontal (HOOP), vertical (VOOP), etc. to indicate that OOP is related to all
or some unknown quantities.
Dope
A
lubricant for threads on pipes.
Double
Two
sections of drill pipe, casing or tubing joined together.
Double block and bleed
A
valving arrangement which ensures no flow in a line, even though the valves may
leak. It consists of two block valves in the main line, with a small bleeder
valve draining the line between the block valves.
Double board
The
name used for the working platform of the derrick man or monkeyboard, when it
is located at a height in the derrick or mast equal to two lengths of pipe
joined together. Compare fourble board and thribble board. See monkeyboard.
Down dip
A
term used where one well is below another well due to inclination of the strata
in which the reservoir lies.
Down
time
Time
during which no drilling or production is possible due to adverse weather
conditions, while downhole equipment is being changed, during well logging,
during mechanical breakdown etc.
Downcomer
A
duct which carries the liquid flowing down a distillation tower from one tray
to the one below it.
Downhole
In a
well bore.
Downhole safety valve
A
valve fitted to the production tube of a well some distance below the sea-bed
in order to permit flow to be stopped in a emergency.
Downstream
A
term referring to industry operations beyond the producing phase of the
business, i.e. refining and marketing.
Draft or draught
The
vertical distance, at any section of a vessel from the surface of the water to
the bottom of the keel. When measured at or near the bow, it is referred to as
draft forward and when measured at or near the stern as draft aft .The mean
draft is the mean of the drafts forward and aft. These drafts are more specifically
described as displacement drafts as opposed to navigational drafts which are
measured to the lowest appendage to the hull as opposed the keel.
Drape structures
This
occurs when sediments are deposited or draped over the physical relief of older
rocks. Such features can include old fault traps or anticlines.
Drawdown
The
total amount that has been borrowed under a given loan agreement.
Draw-down
The
difference between the static formation pressure and the flowing bottom hole
pressure in a well.
Drawworks
The
control centre from which the driller operates the drilling machinery.
Dresser sleeve
A
slip-type collar that connects two lengths of plain-end (threadless) pipe. This
type sleeve connection is used on small-diameter, low pressure lines.
Drift (mandrel)
A
device used to check the inside diameter of casing and tubing before it is run.
See go-devil.
Drift diameter
The
smallest internal diameter of a casing or tubing that is allowed, or the limit
of tolerance. Correspondingly it is the largest diameter of tool or equipment
that can pass through it.
Drill bit
The
part of the drilling tool which actually cuts through the rock.
Drill collars
Lengths
of extra-heavy steel tubing located immediately above the drill bit in order to
maintain pressure on the bit and keep the drill string in tension.
Drill pipe:
See
drill string.
Drill stem
All
members in the assembly used for drilling by the rotary method from the swivel
to the bits, including the kelly, drill pipe and tool joints, drill collars,
stabilisers, and various subsequent items. Compare drill string.
Drill stem test (DST)
A
test whereby the nature and quantity of the formation fluids in a possible oil-
or gas-bearing stratum are determined by allowing them to flow to the surface
through the drill string und(!r carefully controlled conditions.
Drill string
Lengths
of steel tubing roughly
Driller
The
experienced operator who controls the drawworks and heads the drilling crew.
Drilling block
A
lease or a number of leases of adjoining tracts of land that constitute a unit
of acreage sufficient to justify the expense of drilling a wildcat.
Drilling centre
Central
reference point on the drilling deck of a platform from which the co-ordinates
of each centre point of a drilling conductor is measured.
Drilling contractor
A
company that undertakes to provide the equipment and manpower needed to drill a
well on behalf of an operator.
Drilling crew
The
team who actually work on or above the derrick floor during drilling operations
generally a driller plus four roughnecks.
Drilling engineer
The
engineer who designs the casing and is responsible for the drilling programme
for a well.
Drilling floor
See
derrick floor.
Drilling fluid
Circulating
fluid, one function of which is to force cuttings out of the well bore and to
the surface. While a mixture of clay, water, and other chemical additives is
the most common drilling fluid, wells can also be drilled using air, gas, or water
as the drilling fluid. Also called circulating fluid. See mud.
Drilling foreman
The
supervisor of drilling operations on a rig; also the tool pusher or rig
superintendent.
Drilling jars
A
jointed section in a string of cable tools made with slack or play between the
joints. If the bit becomes lodged in the hole, the sudden jar or impact
developed by taking up the slack in the jars aids in freeing the bit.
Drilling line
The
wire rope connecting the drawworks, crown block and travelling block that is
used to raise or lower drill pipe or casing from or into a well.
Drilling mud
A
mixture of clays, water and chemicals pumped down the drill string and up the
annulus during drilling in order to lubricate the system, carry away rock
cuttings, maintain the required pressure at the bit end, provide an aid to
formation evaluation, etc.
Drilling platform
An
offshore platform used to drill exploration and development wells but lacking
the processing facilities of a production platform.
Drilling rate
The speed
with which the bit drills the formation; usually called the rate of
penetration.
Drilling rig
The
complete machinery and structures needed for drilling a well.
Drilling
spool
A
spool with side outlets for kill and choke lines fitted between the BOP stack
and the wellhead.
Drilling table
The
table on the derrick floor whereby the drill pipe is rotated; also called the
rotary table.
Drill-ship
A
ship fitted with a drilling derrick that is used to drill in waters that are
too deep for a jack-up or semi-submersible rig.
Dropcorer
Soil
sampling device lowered to sea-bed and using freefall momentum to penetrate;
produced cores up to three metres long used for soil analysis (geotechnical).
Drum
Container
used for storing and transporting chemicals.
Dry gas
Hydrocarbon
gas from which the readily liquefiable components are either naturally absent
or have been removed by separation and processing. Adefined gas containing
hydrocarbon components upto C4 only as well as inerts (e.g. H2S, hydrocarbon,
nitrogen, etc.)
Dry hole
A
well drilled without finding gas or oil in commercial quantities.
Dry natural gas
Natural
gas which is low in associated liquids; mostly methane.
Dry tree
A
subsea wellhead where the equipment is enclosed in a water-tight chamber.
Drying heights
Heights
above sounding datum, of any areas (banks, foreshores, rocks etc.) which dry at
low water.
DSV
Diving support vessel.
Dual completion
A
mechanical arrangement within the well so that production can be taken
separately and/or simultaneously from two reservoirs. Often two strings of
tubing are run within one production string of casing to provide production
outlets from two perforated intervals which are separated by packers. This is
often called sliding sleeve completion.
Duplex
A
method in which telecommunication between two stations can take place in both
directions simultaneously.
Duplexer
A
switching device used to connect a transmitter and a receiver to the same
antenna.
Duster
A
completely dry hole; a well that encounters neither gas nor liquid at total
depth.
Dutchman
The
threaded portion of a length of pipe or nipple twisted or broken off inside a
collar or other threaded fitting. Threads thus "lost" in a fitting
have to be cut out with a chisel or cutting torch.
Dyna-driII
A
downhole motor driven by drilling fluid that imparts rotary motion to a
drilling bit connected to the tool, thus eliminating the need to turn the
entire drill stem to make hole. The Dyna-Drill, a trade name, is used in
straight and directional drilling.
Dynamic positioning
The
method whereby a vessel is kept on station by computer-controlled thruster
propellers rather than by anchors.
Dynamometer
The
surface, or polished rod dynamometer is a tool which records the resultant of
all forces acting along the axis of the polished rod at any particular instant
of time during one pumping stroke of a pumping unit. This load curve is
recorded with respect to polished rod position.
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