| darcy |
n:a unit of measure of
permeability. A porous medium has a permeability of 1 darcy when differential
pressure of 1 atmosphere across a sample 1 centimeter long and 1 square centimeter in
cross section will force a liquid of 1 centipoise of viscosity through the sample at the
rate of 1 cubic centimeter per second. The permeability of reservoir rocks is usually so
low that it is measured in millidarcys. |
| dart |
a device, similar to a pumpdown
ball, used to manipulate hydraulically operated downhole tools. |
| dart-type inside blowout preventer |
a dart-shaped drill pipe inside
blowout preventer installed on top of the drill stem when the well is kicking through the
drill stem. It is stabbed in open then closed against pressure. |
| dead man |
a piece of wood or concrete,
usually buried, to which a wire guy line is attached for bracing a mast or tower. |
| dead well |
a well that will not flow. |
| debug |
to detect, locate and remove
mistakes from a routine or malfunctions from a computer. |
| deflection |
a change in the angle of a
wellbore. In directional drilling, it is measured in degrees from the vertical |
| deflocculation |
the dispersion of solids that have
stuck together in drilling fluid, usually by means of chemical thinners. See flocculation. |
| defoamer |
any chemical that prevents of
lessens frothing or foaming in another agent. |
| degasser |
the device used to remove unwanted
gas from a liquid, especially from drilling fluid. |
| dehydrate |
to remove water from a substance.
Dehydration of crude oil is normally accomplished by treating with emulsion
breakers. The water vapor in natural gas must be removed to meet pipeline
requirements; a typical maximum allowable water vapor content is 7 pounds per million
cubic feet per day. |
| dehydration |
the removal of water or water
vapor from gas or oil |
| deliquescence |
the liquefaction of a solid
substance due to the solution of the solid by absorption of moisture from the air. |
| density |
the mass or weight of a substance
per unit volume. For instance, the density of a drilling mud may be 10 pounds per
gallon (ppg), 74.8 pounds per cubic foot (lb/ft), or 1,198.2 kilograms per cubic meter
(kg/m3). Specific gravity, relative density, and API gravity are other
units of density. |
| depletion |
A deduction allowed in computing
the taxable income from oil and gas wells. |
| depletion
allowance |
a reduction in US taxes for owners
of an economic interest in minerals in place to compensate for the exhaustion of an
irreplaceable capital asset. This economic interest includes mineral interest,
working interest in a lease, royalty, overriding royalty, production payment interest, and
net profits interest. |
| depreciation |
1. decrease in value of an asset
such as a plant or equipment due to normal wear or passing of time; real property (land)
does not depreciate. 2. an annual reduction of
income reflecting the loss in useful value of capitalized investments by reason of wear
and tear. The concept of depreciation recognizes that the purchase of an asset other
than land will benefit several accounting cycles (periods) and should be expensed
periodically over its useful life. |
| depthometer |
a device used to measure the depth
of a well or the depth at a specific point in a well (such as to the top of a liner or to
a fish) by counting the turns of a calibrated wheel rolling on a wireline as it is lowered
into or pulled out of the well. |
| derrick |
a large load-bearing structure,
usually of bolted construction. In drilling, the standard derrick has four legs
standing at the corners of the substructure and reaching to the crown block. The
substructure is an assembly of heavy beams used to elevate the derrick and provide space
to install blowout preventers, casingheads, and so forth. Because the standard
derrick must be assembled piece by piece, it has largely been replaced by the mast, which
can be lowered and raised without disassembly. |
| derrickman |
the crew member who handles the
upper end of the drill string as it is being hoisted out of or lowered into the hole.
He is also responsible for the circulating machinery and the conditioning of the
drilling fluid. |
| desander |
a centrifugal device for removing
sand from drilling fluid to prevent abrasion of the pumps. It may be operated
mechanically or by a fast-moving stream of fluid inside a special cone-shaped vessel.
Compare desilter. |
| desilter |
a centrifugal device for removing
very fine particles, or silt, from drilling fluids to keep the amount of solids in the
fluid at the lowest possible point. Usually, the lower the solids content of mud,
the faster is the rate of penetration. The desilter work on the same principle as a
desander. Compare desander. |
| development
well |
1. a well drilled in proven
territory in a field to complete a pattern of production. 2. an exploitation well. See exploitation well. |
| deviation |
departure of the wellbore from the
vertical, measured by the horizontal distance from the rotary table to the target.
The amount of deviation is a function of the drift angle and hole depth. The term is
sometimes used to indicate the angle from which a bit has deviated from the vertical
during drilling. See drift angle. |
| 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-survey, or drift-survey, instruments: one reveals the drift angle; the
other indicates both the angle and the direction of deviation. |
| diameter |
the distance across a circle,
measured through its center. In the measure of pipe diameters, the inside diameter
is that of the interior circle and the outside diameter that of the exterior circle. |
| diatomaceous
earth |
an earthy deposit made up of the
siliceous cell walls of one-celled marine algae called diatoms. It is used as an
admixture for cement to produce a low-density slurry. |
| die |
n. a tool used to shape, form, or
finish other tools or pieces of metal. For example, a threading die is used to cut
threads on pipe. |
| die collar |
n: a collar or coupling of tool
steel, threaded internally, that can be used to retrieve pipe from the well on fishing
jobs; the female counterpart of a taper tap. The die collar is made up on the drill
pipe and lowered into the hole until it contacts the lost pipe. If the lost pipe is
stuck so that it cannot rotate, rotation of the die collar on top of the pipe cuts threads
on the outside of the pipe, providing a firm attachment. The pipe is then retrieved
from the hole. Compare taper tap. It is not often used because it is difficult
to release it from the fish should it become necessary. |
| diesel-electric
power |
the power supplied to a drilling
rig by diesel engines driving electric generators; used widely. |
| diesel
engine |
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-oil
plug |
see gunk
plug |
| differential displacing valve |
a special-purpose valve used to
facilitate spacing out and ranging up the well, run in on the tubing string. |
| differential
pressure |
the difference between two fluid
pressures; for example, the difference between the pressure in a reservoir and in a
wellbore drilled in the reservoir, or between atmospheric pressure at sea level and at
10,000 feet. |
| differential
sticking |
a condition in which the drill
stem becomes stuck against the wall of the wellbore because part of the drill stem
(usually the drill collars) has become embedded in the filter cake. necessary
conditions for differential-pressure sticking, or wall sticking, are a permeable formation
and a pressure differential across a nearly impermeable filter cake and drill stem. Also
called wall sticking.
See differential pressure, filter cake. |
| diffusion |
1. the spontaneous movement and
scattering of particles of liquids, gases, or solids. 2. the migration of dissolved substances from an area of high concentration to an
area of low concentration. |
| dilatant
fluid |
a dilatant, or inverted plastic,
fluid is usually made up of a high concentration of well-dispersed solids that exhibits a
nonlinear consistency curve passing through the origin. The apparent viscosity
increases instantaneously with increasing rate of share. The yield point, as
determined by conventional calculations from the direct-indicating viscometer readings, is
negative; however, the true yield point is zero. |
| diluent |
liquid added to dilute or thin a
solution |
| direct-indicating viscometer |
commonly called a "V-G
meter." A rotational device powered by means of an electric motor or handcrank. Used
to determine the apparent viscosity, plastic viscosity, yield point, and gel strengths of
drilling fluids. See direct-reading
viscometer |
| directional
drilling |
intentional deviation of a
wellbore from the vertical. Although wellbores are normally drilled vertically, it
is sometimes necessary or advantageous to drill at an angle from the vertical.
Controlled directional drilling makes is possible to reach subsurface areas laterally
remote from the point where the bit enters the earth. It often involves the use of
turbodrills, Dyna-Drills, whipstocks, or other deflecting rods. |
| directional
survey |
a logging method that records rift
angle, or deflection from the vertical, and direction of the drift. A single-shot
directional-survey instrument makes a single photograph of a compass reading of the draft
direction and the number of degrees the hole is off vertical. A multishot survey
instrument obtains numerous readings in the hole as the device is pulled out of the well.
See directional drilling. |
| direct-reading viscometer |
commonly called a "V-G
meter." The instrument is a rotational-type device powered by means of an electric
motor or handcrank, and is used to determine the apparent viscosity, plastic viscosity,
yield point, and gel strengths (all of which see) of drilling fluids. The usual
speeds are 600 and 300 revolutions per minute. See API RP13B for operational procedures.
Also see direct-indicating
viscometer. |
| dispersant |
a substance added to cement that
chemically wets the cement particles in the slurry, allowing the slurry to flow easily
without much water. |
| dispersed
phase |
that part of a drilling mud--clay,
shale, barite, and other solids--that is dispersed throughout a liquid or gaseous medium,
forming the mud. |
| dispersion |
1. a suspension of extremely fine
particles in a liquid (such as colloids in a colloidal solution). 2. of aggregates, subdivision of aggregates. Dispersion
increases the specific surface of the particle; hence, it results in an increase in
viscosity and gel strength. |
| dispersoid |
a colloid or finely divided
substance. |
| displacement |
1. the weight of a fluid (such as
water) displaced by a freely floating or submerged body (such as an offshore drilling
rig). if the body floats, the displacement equals the weigh of the body. 2. replacement of one fluid by another in the pore space of a
reservoir. For example, oil may be displaced by water. |
| disposal
well |
a well through which water
(usually salt water) is returned to subsurface formations. |
| dissociation |
the separation of a molecule into
two or more fragments (atoms, ions) by interaction with another body or by the absorption
of electromagnetic radiation. |
| dissolved
gas |
natural gas which is in solution
with crude oil in the reservoir. |
| distillation |
the process of driving off gas or
vapor from liquids or solids, usually by heating, and condensing the vapor back to liquid
to purify, fractionate, or form new products. |
| diverter |
a device used to direct fluid
flowing from a well away from the drilling rig. When a kick is encountered at
shallow depths, the well often cannot be shut in safely; therefore, a diverter is used to
allow the well to flow through a side outlet (a diverter line). |
| dizzy nut |
a mechanism used in packers to
lock components together. |
| dog |
a spring-loaded finger in a tubing
end locator. |
| doghouse |
a small house used for keeping
lease records, changing clothes, or any other use around a lease. |
| dog leg |
a bend in pipe, a ditch, or a
well. |
| dolomite |
a type of sedimentary rock similar
to limestone but containing more than 50 percent magnesium carbonate; sometimes a
reservoir rock for petroleum. |
| dome |
a geologic structure resembling an
inverted bowl; a short anticline that plunges on all sides. |
| dome plug
trap |
a reservoir formation in which
fluid or plastic masses of rock material originated at unknown depths and pierced or
lifted the overlying sedimentary strata. |
| donkey pump |
any little pump; used for many
kinds of small temporary pumping operations. |
| dope |
material used on threads of pipe
or tubing to lubricate and prevent leakage. |
| double |
two lengths or joints of pipe
joined together. |
| double grip |
a tool employing tripping devices
that limit tool movement from pressure either above or below the tool |
| double-post
mast |
a well-servicing unit whose mast
consists of two steel tubes. Double-pole masts provide racking platforms for
handling rods and tubing in stands and extend from 65 to 67 feet (20 meters) so that rods
can be suspended as 50-foot (15 meter) doubles and tubing set back as 30-foot (9-meter)
singles. See pole mast. |
| doughnut |
a ring of wedges that supports a
string of pipe or a threaded, tapered ring used for the same purpose. |
| dovetail |
a cutout section in a cone
enabling positive slip movement without the aid of conventional slip return springs |
| downcomer |
a pipe through which flow is
downward. |
| downhole |
pertaining to the wellbore. |
| dozer |
a powered machine for earthwork
excavations. |
| draft |
the vertical distance between the
bottom of a vessel floating in water and the waterline. |
| drag bit |
any of a variety of drilling bits
that have no moving parts. As they are rotated on bottom, elements of the bit make
hole by being pressed into the formation and being dragged across it. See fishtail bit. |
| drag blocks |
spring-loaded buttons on a packer
that provide friction with casing to retard movement of one section of a packer while
another section rotates for setting. |
| drawworks |
the hoisting mechanism on a
drilling rig. It is essentially a large winch that spools off or takes in the
drilling line and thus raises or lowers the drill stem and bit. |
| dress |
to sharpen, repair, or add
accessories to items of equipment (such as drilling bits and tool joints). |
| dresser
sleeve |
a slip-type collar that is used to
join plain-end pipe. |
| drift |
1. an ocean current's speed of
motion. 2. an observed change, usually
uncontrolled, in meter performance, meter factor, etc., that occurs over a period of
time.
v:1. to move slowly out of alignment, off center, or out of
register.
2. gauge or measure pipe by means of a mandrel passed
through it to ensure the passage of tools, pumps, and so on. |
| drifter |
a worker who never stay long in
one place. |
| drift angle |
the angle at which a wellbore
deviates from the vertical, expressed in degrees, as revealed by a directional survey.
Also called angle of deviation, angle of drift, and inclination. See directional
survey. |
| drill |
to bore a hole in the earth,
usually to find and remove subsurface formation fluids such as oil and gas. |
| drillable |
pertaining to packers and other
tools left in the wellbore to be broken up later by the drill bit. Drillable
equipment is made of cast iron, aluminum, plastic, or other soft, brittle material. |
| drill bit |
the cutting or boring element used
for drilling. See bit. |
| drillable
squeeze packer |
a permanent packer, drillable in
nature, capable of withstanding extreme working pressures, for remedial work. It has
a positive flow-control valve built in. |
| drill
collar |
a heavy, thick-walled tube,
usually steel, used between the drill pipe and the bit in the drill stem to provide a
pendulum effect to the drill stem and weight to the bit. |
| drilled
show |
oil or gas in the mud circulated
to the surface |
| drill pipe |
heavy seamless tubing used to
rotate the bit and circulate the drilling fluid. Joints of pipe approximately 30
feet (9 meters) long are coupled together by means of tool joints. |
| drill ship |
a self-propelled floating offshore
drilling unit that is a ship constructed to permit a well to be drilled from it.
While not as stable as Semisubmersible, drill ships are capable of drilling exploratory
wells in deep, remote waters. They may have a ship hull, a catamaran hull, or a
trimaran hull. See floating
offshore drilling rig. |
| drill stem |
all members in the assembly used
for rotary drilling from the swivel to the bit, including the kelly, drill pipe and tool
joints, drill collars, stabilizers, and various specialty items. Compare drill string. |
| drill
string |
the column, or string, of drill
pipe with attached tool joints that transmits fluid and rotational power from the kelly to
the drill collars and bit. Often, especially in the oil patch, the term is loosely
applied to both drill pipe and drill collars. Compare drill
stem. |
| driller |
the employee directly in charge of
a drilling or workover rig and crew. His main duty is operation of the drilling and
hoisting equipment, but he is also responsible for downhole condition of the well,
operation of downhole tools, and pipe measurements. |
| 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
break |
a sudden increase in the drill
bit's rate of penetration. it sometimes indicates that the bit has penetrated a
high-pressure zone and thus warns of the possibility of a kick. |
| drilling
contractor |
an individual or group of
individuals that own a drilling rig and contract their services for drilling wells. |
| drilling
crew |
a driller, a derrickman, and two
or more helpers who operate a drilling or workover rig for one tour each day. |
| drilling
fluid |
circulating fluid, one function of
which is to force cuttings out of the wellbore and to the surface. Other functions
are to cool the bit and to counteract downhole formation pressure. While a mixture
of barite, clay, water, and chemical additives is the most common drilling fluid, wells
can also be drilled by using air, gas, water, or oil-base mud as the drilling fluid.
See mud. |
| drilling fluid cycle time |
a cycle, or down the hole and
back, is the time required for the pump to move the drilling fluid in he hole. The
cycle in minutes equals the barrels of mud in the hole divided by barrels per minute. |
| drilling
foreman |
the supervisor of drilling or
workover operations on a rig. Also called a rig manager, rig supervisor, rig
superintendent, or tool pusher. |
| drilling in |
the operation during the drilling
procedure at the point of drilling into the pay formation. |
| drilling
line |
a wire rope used to support the
drilling tools. Also called the rotary line. |
| drilling
mud |
a specially compounded liquid
circulated through the wellbore during rotary drilling operations. See mud. |
| drilling
out |
1. the operation during the
drilling procedure when the cement is drilled out of the casing and the wellbore after the
casing has been cemented. 2. to remove the
settlings and cavings that are plugged inside a hollow fish (such as drill pipe) during a
fishing operation. |
| drilling
platform rig |
See platform rig. |
| drilling
slot |
See keyway. |
| drilling
spool |
a fitting placed in the blowout
preventer stack to provide space between preventers for facilitating stripping operations,
to permit attachment of choke and kill lines, and for localizing possible erosion by fluid
flow to the spool instead of to the more expensive pieces of equipment. |
| drill out |
1. to remove with the drill bit
the residual cement that normally remains in the lower section of casing and the wellbore
after the casing has been cemented. 2. To
remove the settlings and cavings that are plugged inside a hollow fish (such as drill
pipe) during a fishing operation. |
| drill pipe |
seamless steel or aluminum pipe
made up in the drill stem between the kelly or top drive on the surface and the drill
collars on the bottom. During drilling, it is usually rotated while drilling fluid
is circulated through it. Drill pipe joints are available in three ranges of length:
18 to 22 feet, 27 to 30 feet, and 38 to 45 feet. The most popular length is 27 to 30
feet. It is available with outside diameters ranging from 2 7/8 to 5 1/2 inches.
Several joints are made up (screwed together) to form the drill string. |
| drill
pipe pressure |
the amount of pressure exerted
inside the drill pipe as a result of circulating pressure, entry of formation pressure
into the well, or both. |
| drill pipe pressure gauge |
an indicator, mounted in the mud
circulating system, that measures and indicates the amount of pressure in the drill stem.
See drill stem. |
| drill
pipe slips |
see slips |
| drill ship |
a self-propelled floating offshore
drilling unit that is a ship constructed to permit a well to e drilled from it.
Although not as stable as semisubmersible, drill ships are capable of drilling exploratory
wells in deep, remote waters. See floating
offshore drilling rig. |
| drill stem |
all members in the assembly used
for rotary cutting from the swivel to the ball, including the kelly, drill pipe and tool
joints, drill collars, stabilizers, and various specialty items. Compare drill string. |
| drill
stem safety valve |
a special valve installed below
the kelly. Usually, the valve is open so that drilling fluid can flow out of the
kelly and down the drill stem. It can, however, be manually closed with a special
wrench when necessary. In one case, the valve is closed and broken out, still
attached to the kelly to prevent drilling mud in the kelly from draining onto the rig
floor. In another case, when kick pressure inside the drill stem exists, the drill stem
safety valve is close to prevent the pressure from escaping up the drill stem. |
| drill
stem test (DST) |
the conventional method of
formation testing. The basic drill stem test tool consists of a packer or packers,
valve or ports that may be opened and closed from the surface, and two or more
pressure-recording devices. The tool is lowered on the drill string to the zone to
be tested. The packer or packers are set to isolate the zone from the drilling fluid
column. The valves or ports are then opened to allow for formation flow while the
recorders chart static pressures. A sampling chamber traps dean formation fluids at
the end of the test. Analysis of the pressure charts is an important part of
formation testing. |
| drill
string |
the column, or string, of drill
pipe with attached tool joints that transmits fluid and rotational power form the kelly to
the drill collars and bit. Often, especially in the oil patch, the term is loosely
applied to both drill pipe and drill collars. Compare drill
stem. |
| drill
string float |
a check valve in the drill string
that will allow fluid to be pumped into the well but will prevent flow from entering the
string. |
| drip |
equipment designed to remove small
quantities of liquids from a gas stream. |
| drive
bushing |
see kelly
bushing |
| drive-in
unit |
a type of portable service or
workover rig that is self-propelled, using power from the hoisting engines. The
driver's cab and steering wheel are mounted on the same end as the mast support; thus the
unit can be driven straight ahead to reach the wellhead. See carrier rig. |
| dry gas |
natural gas that is produced
without liquids; also a gas that has been treated to remove all liquids. |
| dry hole |
an exploratory or development well
found to be incapable of producing either oil or gas in sufficient quantities to justify
completion as an oil or gas well. |
| DST |
drill stem test |
| DST tool |
drill stem test tool; used for
formation evaluation. |
| dual
completion |
a single well that produces from
two separate formation at the same time. Production from each zone is segregated by
running two tubing strings with packers inside the single string of production casing, or
by running one tubing string with a packer through one zone while the other is produced
through the annulus. In a miniaturized dual completion, two separate 4 1/2-inch or
smaller casing strings are run and cemented in the same wellbore. |
| dummy valve |
a blanking valve placed in a gas
lift mandrel to block off annular communication to the tubing. |
| dump bailer |
a bailing device with a release
valve, usually of the disk or flapper type, used to place, or spot material (such as
cement slurry) at the bottom of the well. |
| duplex pump |
a reciprocating pump with two
pistons or plungers and used extensively as a mud pump on drilling rigs. |
| dutchman |
a piece of pipe that has been
twisted off inside a female connection; or a short section of material, such as belting or
pipe, used to lengthen existing equipment. |
| DV tool |
a generic term, originally a
trademark name, used to describe a stage tool, used in selective zone primary cementing. |
| Dyna-Drill |
trade name for 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. Used in
straight and directional drilling. |
| dynamic
positioning |
a method by which a floating
offshore drilling rig is maintained in position over an offshore well location without the
use of mooring anchors. Generally, several propulsion units, called thrusters, are
located on the hulls of the structure and are actuated by a sensing system. A
computer to which the system feeds signals directs the thrusters to maintain the rig on
location. |
