Oil & Gas Glossary 1.0

The pressure at the bottom of a well when the surface valves on the well are completely closed. It is caused by formation fluids at the bottom of the well.

2. a hole of a diameter smaller than the main hole and drilled in the bottom of the main hole.

The force that a fluid (liquid or gas) exerts uniformly in all directions within a vessel, pipe, hole in the ground, and so forth, such as that exerted against the inner wall of a tank or that exerted on the bottom of the wellbore by a fluid. Pressure is expressed in terms of force exerted per unit of area, as pounds per square inch, or in kilopascals.

The amount of pressure that, when applied inside a string of casing, causes the wall of the casing to fail. This pressure is critically important when a gas kick is being circulated out, because gas on the way to the surface expands and exerts more pressure than it exerted at the bottom of the well.

A measure of the density of a drilling fluid expressed as pounds per gallon, pounds per cubic foot, or kilograms per cubic meter. Mud weight is directly related to the amount of pressure the column of drilling mud exerts at the bottom of the hole.

A drilling method in which the hole is drilled by dropping a sharply pointed bit on bottom. The bit is attached to a cable, and the cable is repeatedly dropped as the hole is drilled.

Pressure at the bottom of a well that is shut in.

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.

A sudden, usually short-duration, increase in pressure. When pipe or casing is run into a hole too rapidly, an increase in the hydrostatic pressure results, which may be great enough to create lost circulation

1. a passageway through jet bits that causes the drilling fluid to be ejected from the bit at high velocity. The jet of mud clears the bottom of the hole. Nozzles come in different sizes that can be interchanged on the bit to adjust the velocity with which the mud exits the bit.

To install a pump or pumping unit, sucker rods, and bottom-hole pump.

A device that prevents leakage along a piston, rod, propeller shaft, or other moving part that passes through a hole in a cylinder or vessel. It consists of a box or chamber made by enlarging the hole and a gland containing compressed packing. On a well being artificially lifted by means of a sucker rod pump, the polished rod operates through a stuffing box, preventing escape of oil and diverting it into a side outlet to which is connected the flow line leading to the oil and gas separator or to the field storage tank. For a bottomhole pressure test, the wireline goes through a stuffing box and lubricator, allowing the gauge to be raised and lowered against well pressure. The lubricator provides a pressure-tight grease seal in the stuffing box.

Generally, the first string of casing in a well. It may be lowered into a hole drilled into the formations near the surface and cemented in place; it may be driven into the ground by a special pile driver (in such cases, it is sometimes called drive pipe); or it may be jetted into place in offshore locations. Its purpose is to prevent the soft formations near the surface from caving in and to conduct drilling mud from the bottom of the hole to the surface when drilling starts. Also called conductor pipe.

Generally, the first string of casing in a well. It may be lowered into a hole drilled into the formations near the surface and cemented in place; or it may be driven into the ground by a special pile drive (in such cases, it is sometimes called drive pipe); or it may be jetted into place in offshore locations. Its purpose is to prevent the soft formations near the surface from caving in and to conduct drilling mud from the bottom of the hole to the surface when drilling starts. Also called conductor pipe.

To release pipe that is stuck in the hole by running washover pipe. The washover pipe must have an outside diameter small enough to fit into the borehole but an inside diameter large enough to fit over the outside diameter of the stuck pipe. A rotary shoe, which cuts away the formation, mud, or whatever is sticking the pipe, is made up on the bottom joint of the washover pipe, and the assembly is lowered into the hole. Rotation of the assembly frees the stuck pipe. Several washovers may have to be made if the stuck portion is very long.

The ratio between the pressure in the hole and the operating-piston pressure needed to close the rams of a blowout preventer.

The component in a blowout preventer that cuts, or shears, through drill pipe and forms a seal against well pressure. Shear rams are used in floating offshore drilling operations to provide a quick method of moving the rig away from the hole when there is no time to trip the drill stem out of the hole.

The small amount of additional mud weight carried over that needed to balance formation pressure to overcome the pressure-reduction effects caused by swabbing when a trip out of the hole is made.

A preventer having a unit of packing material whose closure depends on well pressure coming from below. It is used primarily to strip pipe through the hole or allow pipe to be moved with pressure on the annulus.

A short cylindrical device installed in the drill stem between the bottom-most drill collar and a downhole motor. Its purpose is to deflect the downhole motor off vertical to drill a directional hole. See drill stem.

A short, heavy, cylindrical steel section with a rounded bottom and attached to the bottom of the casing string. It contains a check valve and functions similarly to the float collar but also serves as a guide shoe in the casing.

A block with lead or another relatively soft material on its bottom. It is made up of drill pipe or tubing at the surface, run into a well, and set down on the object that has been lost in the well. The block is retrieved and the impression is examined. The impression is a mirror image of the top of the fish and indicates the fish's position in the hole, i.e., whether it is centered or off to one side. From this information, the correct fishing tool can be selected.

Drilling in which the size of the hole is smaller than the conventional hole diameter for a given depth. This decrease in hole size enables the operator to run smaller casing, thereby lessening the cost of completion. See miniaturized completion.

1. a tool placed on a drill collar near the bit that is used, depending on where it is placed, either to maintain a particular hole angle or to change the angle by controlling the location of the contact point between the hole and the collars. See packed-hole assembly.

A process used to repair a hole in the casing by pumping cement down tubing or drill pipe. First, the casinghead, or bradenhead, is closed to prevent fluids from moving up the casing. Then the rig's pumps are started. Pump pressure moves the cement out of the tubing or pipe and, since the top of the casing is closed, the cement goes into the hole in the casing. The tubing or pipe is pulled from the well and the cement allowed to harden. The hardened cement seals the hole in the casing. Although the term "bradenhead squeezing" is still used, the term "bradenhead" is obsolete. See annular space, casinghead, squeeze.

An item of production equipment used to separate liquid components of the well stream from gaseous elements. Separators are either vertical or horizontal and either cylindrical or spherical in shape. Separation is accomplished principally by gravity, the heavier liquids falling to the bottom and the gas rising to the top. A float valve or other liquid-level control regulates the level of oil in the bottom of the separator.

One of several valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and drill pipe or in open hole (i.e., hole with no drill pipe) during drilling completion operations. Blowout preventers on land rigs are located beneath the rig at the land's surface; on jackup or platform rigs, at the water's surface; and on floating offshore rigs, on the seafloor.

The course of drilling fluid downward through the annulus and upward through the drill stem, in contrast to normal circulation in which the course is downward through the drill stem and upward through the annulus. Seldom used in open hole, but frequently used in workover operations. Also referred to as "circulating the short way," since returns from bottom can be obtained more quickly than in normal circulation.

A device that is fastened to the outside of casing to remove mud cake from the wall of a hole to condition the hole for cementing. By rotating or moving the casing string up and down as it is being run into the hole, the scratcher, formed of stiff wire, removes the cake so that the cement can bond solidly to the formation.

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.

1. to move the drill stem up and down in the hole over a short distance without rotation. Careless execution of this operation creates pressure surges that can cause a formation to break down, resulting in lost circulation.

A small mud tank with a capacity of 10 to 15 barrels, usually with 1-barrel or H-barrel divisions, used to ascertain the amount of mud necessary to keep the wellbore full with the exact amount of mud that is displaced by drill pipe. When the bit comes out of the hole, a volume of mud equal to that which the drill pipe occupied while in the hole must be pumped into the hole to replace the pipe. When the bit goes back in the hole, the drill pipe displaces a certain amount of mud, and a trip tank can be used again to keep track of this volume.

An instrument that measures fluid pressure and usually registers the difference between atmospheric pressure and the pressure of the fluid by indicating the effect of such pressures on a measuring element (e.g., a column of liquid, pressure in a Bourdon tube, a weighted piston, or a diaphragm).

Pressure exceeding or falling below the normal pressure to be expected at a given depth. Normal pressure increases approximately 0.465 psi per foot of depth (10.5kPa per meter of depth). Thus, normal pressure at 10,000 feet is 4,650 psi; abnormal pressure at this depth would be higher or lower than 4,650 psi. See pressure gradient.

A type of mobile offshore drilling unit that has a part of its structure in contact with the seafloor when it is on site and drilling a well. The remainder of the rig is supported above the water. The rig can float, however, allowing it to be moved from one drill site to another. Bottom-supported units include submersible rigs and jackup rigs. See mobile offshore drilling unit.

The average pressure within the reservoir at any given time. Determination of this value is best made by bottomhole pressure measurements with adequate shut-in time. If a shut-in period long enough for the reservoir pressure to stabilize is impractical, then various techniques of analysis by pressure buildup or drawdown tests are available to determine static reservoir pressure.

A test that measures the reservoir pressure of the well, obtained at a specific depth or at the midpoint of the producing zone. A flowing bottomhole pressure test measures pressure while the well continues to flow; a shut-in bottomhole pressure test measures pressure after the well has been shut in for a specified period of time. See bottomhole pressure, bottomhole pressure gauge.

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.

A method of determining the amount of pressure that is allowed to appear on the casing pressure gauge as a kick is circulated out of a well. In general, it is determined by slowly pumping mud into the well while it is shut in and observing the pressure at which the formation begins to take mud.

A device made up in the drill stem above the mill to collect bits of junk ground away during a milling operation. During milling, drilling mud under high pressure forces bits of junk up the narrow space between the boot sub and the hole wall. When the junk reaches the wider annulus above the boot sub and pressure drops slightly, the junk falls into the boot sub. A boot sub also can be run above the bit during routine drilling to collect small pieces of junk that may damage the bit or interfere with its operation.

A bell-shaped hole dug beneath a pipeline to provide room for use of tools.

A bottomhole assembly consisting of stabilizers and large-diameter drill collars arranged in a particular configuration to maintain drift angle and direction of a hole.

Total pressure measured from an absolute vacuum. It equals the sum of the gauge pressure and the atmospheric pressure corresponding to the barometer (expressed in pounds per square inch).

A blowout preventer that uses rams to seal off pressure on a hole that is with or without pipe. Also called a ram preventer.

To pump a designated quantity of a substance (such as acid or cement) into a specific interval in the well. For example, 10 barrels of diesel oil may be spotted around an area in the hole in which drill collars are stuck against the wall of the hole in an effort to free the collars.

In pipeline construction, the hole drilled as the first step of a directionally drilled river crossing. It establishes a pathway for the pipeline.

Of or relating to the bottom waters of the ocean.

A complete trip from the bottom of the wellbore to the top

2. the amount of pressure indicated by a drill pipe pressure gauge when drilling fluid is being circulated by the mud pump. Pressure losses occur as the fluid is circulated.

Total pressure exerted in the wellbore by a column of fluid and/or back-pressure imposed at the surface.

The lowest extremity of the tool to which accessories or other tools can be coupled.

Said of any pressure-tight vessel or container when the internal pressure is lower than atmospheric 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.

The vertical distance between the bottom of a vessel floating in water and the waterline.

Tubular components attached to the bottom of a packer to extend it bore.

A low platform mounted on the bottom of equipment for ease of moving, hauling, or storing.

A fluid moving as a unit in which all shear stress occurs at the pipe wall and hole wall. The stream thus assumes the shape of several telescopic layers of fluid with lowest velocities near the pipe and hole walls and the fastest in the middle.

2. the change (along a horizontal distance) in atmospheric pressure. Isobars drawn on weather maps display the pressure gradient.

A method of preparing a well for production in which no production casing or liner is set opposite the producing formation. Reservoir fluids flow unrestricted into the open wellbore. An open-hole completion has limited use in rather special situations. Also called a barefoot completion.

A pressure-fight container (bomb) used to record the pressure in a well at a point opposite the producing formation

A cast-iron or magnesium drillable tool consisting of a packing assembly and a back-pressure valve. It is used to close off the annular space between tubing or drill pipe and casing to allow the placement of cement or fluid through the tubing or drill pipe at any predetermined point behind the casing or liner, around the shoe, or into the open hole around the shoe.

Drill pipe, drill collars, casing, or tubing that has inadvertently become immovable in the hole. Sticking may occur when drilling is in progress, when casing is being run in the hole, or when the drill pipe is being hoisted.

The increase in bottomhole pressure expressed as an increase in pressure that occurs only when mud is being circulated. Because of friction in the annulus as the mud is pumped, bottomhole pressure is slightly, but significantly, higher than when the mud is not being pumped. ECD is calculated by dividing the annular pressure loss by 0.052, dividing that by true vertical depth, and adding the result to the mud weight.

To pump drilling fluid into the wellbore while the pipe is being withdrawn to ensure that the wellbore remains full of fluid even though the pipe is withdrawn. Filling the hole lessens the danger of a kick or of caving of the well or the wellbore.

Repressuring of an oil-field to maintain original pressure. The use of water flooding or natural gas recycling during primary recovery to provide additional formation pressure and displacement energy that can supplement and conserve natural reservoir drives. Although commonly begun during primary production, pressure maintenance methods are often considered to be a form of enhanced oil recovery.

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.

1. a scale of pressure differences in which there is a uniform variation of pressure from point to point. For example, the pressure gradient of a column of water is about 0.433 pounds per square inch per foot (9.794 kilopascals per meter) of vertical elevation. The normal pressure gradient in a formation is equivalent to the pressure exerted at any given depth by a column of 10 percent salt water extending from that depth to the surface 0.465 pounds per square inch per foot or 10.518 kilopascals per meter).

A borehole; the hole drilled by the bit. A wellbore may have casing in it or it may be open (uncased); or part of it may be cased, and part of it may be open. Also called a borehole or hole.

2. to recover bottomhole fluids, samples, mud, sand, or drill cuttings by lowering a cylindrical vessel called a bailer to the bottom of a well, filling it, and retrieving it.

2. in reference to an anchor, to fail to hold on a soft bottom, pulling out, instead, with a large ball of mud attached.

To pull the bottom end of a sucker rod away from a well when laying rods down.

The pressure at which a well is circulated during well-killing procedures after killweight mud has filled the drill stem. This pressure is maintained until the well is completely filled with killweight mud.

To have too long a length of rods between the pumping unit and the pump seat so that the pump hits bottom on the down stroke.

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.

A tube mounted at the bottom of a sucker rod pump and inside a gas anchor to provide a conduit into the pump for well fluids that contain little or no gas.

A tubular device, usually from 10 to 60 feet (3 to 18 meters) long, run at the bottom of the drill pipe in place of a bit and used to cut a core sample.

A valve in the bottom of a retainer. See wireline.

Water found below oil and gas in a producing formation

2. a device for guiding pipe and lowering it to the water bottom as it is being laid down by a lay barge. It is hinged to permit adjustments in the angle of pipe launch.

A workover performed with a continuous steel tube, normally 3/4 inch to 1 inch outside diameter, which is run into the well in one piece inside the normal tubing. Lengths of the tubing up to 16,000 feet are stored on the surface on a reel in a manner similar to that used for wireline. The unit is rigged up over the wellhead. The tubing is injected through a control head that seals off the tubing and makes a pressure-tight connection. A unique feature of the unit is that it allows continuous circulation while it is being lowered into the hole.

A length of pipe whose bottom edge is serrated or dressed with a hard cutting material and that is run into the wellbore around the outside of stuck casing, pipe, or tubing to mill away the obstruction.

A diagnostic tool used to ascertain whether there is a gas leak in the tubing of a gas lift well. If there is a tubing leak, the pressure on the annulus will equal the pressure on the tubing.

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.

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.

The location of the bottom of a string of casing that is cemented in a well. Typically, a casing shoe is made up on the end of the casing at this point.

A device to measure bottomhole pressure. See bottomhole pressure bomb.

A pressure-sensing element consisting of a twisted or curved rube of non-circular cross section, which tends to straighten when pressure is applied internally. By the movements of an indicator over a circular scale, a Bourdon tube indicates the pressure applied.

1. an automatic valve that opens or closes when an abnormal condition occurs (e.g., a pressure relief valve on a separator that opens if the pressure exceeds the set point, or the shutdown valve at the wellhead that closes if the line pressure becomes too high or too low).

A procedure whereby the formation immediately below the casing shoe is subjected to a pressure equal to the pressure expected to be exerted later by a higher drilling glut density or by the sum of a higher drilling fluid density and back-pressure created by a kick.

3. the operating pressure level measured downstream from a measuring device.

1.a high-pressure gas injected into a formation to maintain or restore reservoir pressure.

1. the pressure maintained on equipment or systems through which a fluid flows.

An equipment's working pressure times a safety factor.

The pressure to which a particular piece of equipment is subjected during normal operations.

The pressure resulting from restriction of full natural flow of oil or gas.

The extent to which the hydrostatic pressure of the mud column exceeds formation pressure.

The pressure generated by the mud pumps and exerted on the drill stem

The pressure at which a well that has been closed in on a kick is circulated when well-killing procedures are begun

Commonly referred to as snubbing; running of tool and/or pulling of tubing under well pressure.

A device for maintaining pressure in a line, downstream from the value.

Of or relating to a condition in which pressure in the wellbore is less than the pressure in the formation.

A loss of pressure that results from friction sustained by a fluid passing through a line, valve, fitting, or other device.

A thick-walled container, usually steel, used to hold devices that determine and record pressure or temperature in a wellbore. See bottomhole pressure.

A formation fluid sampling device, actually run on conductor line rather than wireline, that also logs flow and shut-in pressure in rock near the borehole. A spring mechanism holds a pad firmly against the sidewall while a piston creates a vacuum in a test chamber. Formation fluids enter the tes5t chamber through a valve in the pad. A recorder logs the rate at which the test chamber is filled. Fluids may also be drawn to fill a sampling chamber. Wireline formation tests may be done any number of times during one tip in the hole, so they are very useful in formation testing.

2. to lower or raise tools in or out of a well with pressure inside the well. The term comes from the fact that a lubricant (grease) is often used to provide a seal against well pressure while allowing wireline to move in or out of the well.

Formation fluid pressure equivalent to about 0.465 pounds per square foot of depth from the surface. If the formation pressure is 4,650 pounds per square inch at 10,000 feet, it is considered normal.

A bottomhole pressure test that measures pressure after the well has been shut in for a specified period of time. See bottomhole pressure test.

2. to lower or raise tools in or out of a well with pressure inside the well. The term comes from the fact that a lubricant (grease) is often used to provide a seal against well pressure while allowing wireline to move in or out of the well.

In a well-control operation, closing the BOP without first opening an alternate flow path up the choke line. When the BOP is closed, pressure in the annulus cannot be read on the casing pressure gauge.

Water occurring in a producing formation below the oil or gas in that same formation.

Abbreviation: run-in-hole.

Prevention of formation fluid flow by maintaining a hydrostatic pressure equal to or greater than formation pressure

Additives that, when added to drilling fluid, lubricate bearing surfaces subjected to extreme pressure.

A device that reduces the pressure or volume of a fluid flowing in a line and maintains the pressure or volume at a specified level.

An event occurring when borehole pressure is of such magnitude that the exposed formation cannot withstand applied pressure.

A method of killing a well that has kicked, in which the choke size is adjusted to maintain a constant casing pressure. This method does not work unless the kick is all or nearly all salt water. if the kick is gas, this method will not maintain a constant bottomhole pressure, because gas expands as it rises in the annulus. In any case, it is not a recommended well-control procedure.

Pressure of the annular fluid on the casing at the surface when a well is shut in.

See back-pressure

The force exerted by a body of fluid at rest. It increases directly with the density and the depth of the fluid and is expressed in pounds per square inch or kilopascals. The hydrostatic pressure of fresh water is 0.433 pounds per square inch per foot of depth (9.792 kilopascals per meter). In drilling, the term refers to the pressure exerted by the drilling fluid in the wellbore. In a water drive field, the term refers to the pressure that may furnish the primary energy for production.

The maximum volume of natural gas that can be processed through an absorber at a specified absorption oil rate, temperature, and pressure without exceeding pressure drop or any other operating limitation.

A milling device attached to the bottom of washpipe that mills or drills debris accumulated around the outside of the pipe being washed over. usually, a burn shoe has pieces of very hard tungsten carbide embedded in it. Also called a rotary shoe. See washpipe.

The lowest internal pressure at which a failure (of pipe) will take place.

In drilling, the entrance of formation fluids into the wellbore because hydrostatic pressure is less than formation pressure.

A mobile bottom-supported offshore drilling structure with columnar or open-truss legs that support the deck and hull. When positioned over the drilling site, the bottoms of the legs rest on the seafloor. A jackup rig is towed or propelled to a location w

Abbreviation: pull-out-of-hole

A wellbore in which casing has been run.

To run casing or pipe.

Uncased portion of a well.

The ratio between the pressure required to open the preventer and the well pressure under the rams.

The normal pressure divided by true vertical depth.

A sucker rod string, that is, the entire length of sucker rods, which usually consist of several single rods screwed together. The rod string serves as a mechanical link from the beam pumping unit on the surface to the sucker rod pump near the bottom of the well.

To begin drilling; to start the hole.

A device to provide running the tubing dry with a packer released by elevating tubing pressure, thereby opening the tubing to formation pressure.

The point at which a formation will crack from pressure in the wellbore.

2. of a hole, having no drill pipe or tubing suspended in it.

A wellbore or formation known to contain hydrogen sulfide gas.

A hole made by drilling or boring; a wellbore.

The reservoir drive mechanism in which oil is produced by the expansion of the underlying water and rock, which forces the oil into the wellbore. In general, there are two types of water drive: bottom-water drive, in which the oil is totally underlain by water; and edgewater drive, in which only a portion of the oil is in contact with the water.

The force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although "head" refers to distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic head. Compare hydrostatic pressure.

A hole dug, usually before drilling of a well, to allow working space for the casinghead equipment.

An uncontrolled flow of gas, oil, or other well fluids into the atmosphere or into an underground formation. A blowout, or gusher, can occur when formation pressure exceeds the pressure applied to it by the column of drilling fluid.

Any cementing operation after the primary cementing operation. Secondary cementing includes a plug-back job, in which a plug of cement is positioned at a specific point in the well and allowed to set. Wells are plugged to shut off bottom water or to reduce the depth of the well for other reasons.

2. a valve used to regulate automatically a uniform pressure on the inlet side of the valve.

A pin shaped like a carpenter's nail and placed in a pressure relief valve. When the pin shears, it opens the valve to relieve pressure inside a vessel.

To pass (as a rope) through a hole or opening in a block or similar device.

1. to seal the hole against formation fluids by allowing the buildup of wall cake.

The depth in the hole at which the tubing, casing, or drill pipe is stuck.

To bore a hole in the earth, usually to find and remove subsurface formation fluids such as oil and gas.

2. to force a wireline tool or tubing down the hole by using a reciprocating motion.

2. a hole or opening in a line or vessel into which a gauge or valve may be inserted and screwed tight.

To lower the drill stem, tubing, casing, or sucker rods in to the wellbore.

The pressure in a vessel or container as registered on a gauge attached to the container. This reading does not include the pressure of the atmosphere outside the container.

1. a valve used to regulate back-pressure on equipment or systems through which a fluid flows.

A special steel pumping rod. Several rods screwed together make up the mechanical link from the beam pumping unit on the surface to the sucker rod pump at the bottom of a well. Sucker rods are threaded on each end and manufactured to dimension standards and metal specifications set by the petroleum industry. Lengths are 25 or 30 feet (7.6 or 9.1 meters); diameter varies from 1/2 to 1-1/8 inches (12 to 30 millimeters). There is also a continuous sucker rod (tradename: Corod).

Hydrocarbons which are in the gaseous state under reservoir conditions but which become liquid either in passage up the hole or at the surface.

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.

A threaded nipple with a rounded, closed end used to stop up a hole or close off the end of a line.

An indicator, mounted in the mud circulating system, that measures and indicates the amount of pressure in the drill stem. See drill stem.

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.

A mobile submersible drilling structure constructed of several steel cylinders, or bottles. When the bottles are flooded, the rig submerges and rests on bottom; when water is removed from the bottles, the rig floats. The latest designs of this type of rig drill in water depths up to 100 feet (30.5 meters). See submersible drilling rig.

A device placed or hung in the casing below the blowout preventer stack to form a pressure tight seal. Pressure is then applied to the blowout preventer stack to test it for leaks

2. a tool place in the hole to retain cement or other material; it may later be removed, drilled out, or left permanently.

2. to recover liquid hydrocarbons from natural or refinery gas in a gas-absorption plant. The wet gas enters the absorber at the bottom and rises to the top, encountering a stream of absorption oil (a light oil) traveling downward over bubble-cap trays, valve trays, or sieve trays. The light oil removes, or absorbs, the heavier liquid hydrocarbons from the wet gas.

The pressure lost in a pipeline or annulus due to the velocity of the liquid in the pipeline, the properties of the fluid, the condition of the pipe wall, and the alignment of the pipe. In certain mud-mixing systems, the loss of head can be substantial

Generically, a pressure gauge usually used in lines or manifolds. Many companies make pressure gauges. Cameron, now Cooper Oil Tools, makes many types of gauges.

Pressure of the annular fluid on the casing at the surface when a well is shut in

A phenomenon that sometimes occurs when a well blows out. Rocks, sand, clay, and other debris clog the hole and stop the blowout.

A device used to enlarge the size of an existing borehole, having teeth arranged on its outside circumference to cut the formation as it rotates.

The pressure at which a formation will break down, or fracture.

Gas pressure built up between the casing and tubing.

1. to force pipe or tools into a high-pressure well that has not been killed (i.e., to run pipe or tools into the well against pressure when the weight of pipe is not great enough to force the pipe through the BOPs). Snubbing usually requires an array of wireline bocks and wire rope that forces the pipe or tools into the well through a stripper head or blowout preventer until the weight of the string is sufficient to overcome the lifting effect of the well pressure on the pipe in the preventer. In workover operations, snubbing is usually accomplished by using hydraulic power to force the pipe through the stripping head or blowout preventer.

A rigid offshore drilling platform built of steel-reinforced concrete and used to drill development wells. The platform is floated to the drilling site in a vertical position, and at the site tall caissons that serve as the foundation of the platform are flooded so that the platform submerges and comes to rest on bottom. Because of the enormous weight of the platform, the force of gravity alone keeps it in place. See platform rig.

1. to explode nitroglycerine or other high explosives in a hole to shatter the rock and increase the flow of oil, now largely replaced by formation fracturing.

A special coupling device inserted one or two joints above the bottom of the casing string that contains a check valve to permit fluid to pass downward but not upward through the casing. The float collar prevents drilling mud from entering the casing while it is being lowered, allowing the casing to float during its descent and thus decreasing the load on the derrick or mat. A float collar also prevents backflow of cement during a cementing operation.

The pressure in a well between the casing and the tubing or the casing and the drill pipe.

An entry of water, gas, oil, or other formation fluid into the wellbore during drilling. It occurs because the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the formation drilled. If

A mobile submersible drilling structure consisting of a barge hull that rests on bottom, steel posts that rise from the top of the barge hull, and a deck that is built on top of the posts, well above the waterline. It is used to drill wells in water no deeper than about 30-35 feet (9-10.7m). Most posted barge submersibles work in inland gulfs and bays. See submersible drilling rig.

A wellbore that has been unintentionally drilled in a direction other than vertical. It usually occurs where there is a section of alternating hard and soft strata steeply inclined from the horizontal.

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.

A vertical pipe rising along the side of the derrick or mast, which joins the discharge line leading from the mud pump to the rotary hose and through which mud is pumped going into the hole.

Any object or device that blocks a hole or passageway (such as a cement plug in a borehole).

To prepare the drilling rig for making hole; to install tools and machinery before drilling is started.

The depth in the hole at which the drill stem, tubing, or casing is stuck.

A hole in the side of a tank through which a man can enter the tank, also the cleanout plate.

2. to stand pipe on the derrick floor when pulling it out of the hole.

2. difference between the annular velocity of the fluid and the rate at which a cutting is removed from the hole.

To place cement plugs into a dry hole and abandon it.

A device that stores hydraulic fluid under pressure in special containers and provides a method to open and close the blowout preventers quickly and reliably. Usually, compressed air and hydraulic pressure provide the opening and closing force in the unit. See blowout preventer.

A tool used in drilling to smooth the wall of a well, enlarge the hole to the specified size, help stabilize the bit, straighten the wellbore if kinks or doglegs are encountered, and rill directionally. See ream.

An integral part of a blowout preventer, which serves as the closing element on an open hole. Its ends do not fit around the drill pipe but seal against each other and shut off the space below completely. See ram

A device used with slips to prevent tubing from falling into the hole when a joint of pipe is being unscrewed and racked.

The smaller of the side fittings on a bell nipple, used to fill the hole when drill pipe is being removed from the well.

To use a whipstock, turbodrill, or other mud motor to drill around broken drill pipe or casing that has become lodged permanently in the hole.

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.

A plug in the flow line at the well head which has a small hole drilled through it through which oil flows, and which keeps a well from flowing at too high a rate.

A drilling rig that is used exclusively to drill offshore exploration and development wells and that floats upon the surface of the water when being moved from one drill site to another. It may or may not float once drilling begins. Two basic types of mobile offshore drilling units are used to drill most offshore wildcat wells: bottom-supported drilling rigs and floating drilling rigs.

Clamps that grip a stand of casing, tubing, drill pipe, or sucker rods so that the stand can be raised or lowered into the hole.

1. a hole in the rig floor, 30 to 35 feet (9 to 11 meters) deep, which is lined with casing that projects above the floor and into which the kelly and swivel are placed when hoisting operations are in progress.

The partial or complete collapse of the walls of a hole resulting from internal pressures due primarily to swelling from hydration or formation gas pressures. See caving.

(slang) to cave in; to fail. After a violent blowout, the force of the fluids escaping from the wellbore sometimes blows a large hole in the ground. In this case, the well is said to have cratered. Equipment craters when it falls.

An assembly of tools made up on drill pipe that is lowered into the hole to retrieve lost or stuck equipment. Also call a fish assembly.

A fishing tool containing metal-cutting knives that is lowered into the hole and over the outside of a length of pipe to cut it. The severed part of the pipe can then be brought to the surface.

See open-hole completion

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.

A drilling structure consisting of a barge upon which the drilling equipment is constructed. When moved from one location to another, the barge floats. When stationed on the drill site, the barge can be anchored in the floating mode or submerged to rest on the bottom. Typically, inland barge rigs are used to drill wells in marshes, shallow inland bays, and areas where the water covering the drill site in not too deep. Also called swamp barge. See floating offshore drilling rig.

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.

A valve that opens at a preset pressure to relieve excessive pressures within a vessel or line. Also called a relief valve, safety valve, or safety relief valve.

A sealing device used to close off the annular space around the kelly in drilling with pressure at the surface, usually installed above the main blowout preventers. A rotating head makes it possible to drill ahead even when there is pressure in the annulus that the weight of the drilling fluid is not overcoming; the head prevents the well from blowing out. It is used mainly in the drilling of formations that have low permeability. The rate of penetration through such formations is usually rapid.

A device secured around the casing at the regular intervals to center it in the hole. Casing that is centralized allows a more uniform cement sheath to form around the pipe.

An operation in which a specially blended liquid is pumped down a well and into a formation under pressure high enough to cause the formation to crack open, forming passages through which oil can flow into the wellbore. Sand grains, aluminum pellets, glass beads, or similar materials are carried in suspension into the fractures. When the pressure is released at the surface, the fractures partially close on the proppants, leaving channels for oil to flow through to the well. Compare explosive fracturing.

The smooth, uninterrupted circulation of drilling fluid down the drill stem, out the bit, up the annular space between the pipe and the hole, and back to the surface. Compare reverse circulation.

A hole made in the casing, cement, and formation through which formation fluids enter a wellbore. Usually several perforations are made at a time.

A hole drilled in the earth for purpose of (1) finding or producing crude oil or natural gas; or (2) providing services related to the production of crude oil or natural gas.

1. a rubber disk surrounding drill pipe or tubing that removes mud as the pipe is brought out of the hole.

A method of stimulating production by opening new flow channels in the rock surrounding a production well. Often call a frac job. Under extremely high hydraulic pressure, a fluid (such as distillate, diesel fuel, crude oil, dilute hydrochloric acid, water, or kerosene) is pumped downward through production tubing or drill pipe and forced out below a packer or between two packers. The pressure causes cracks to open in the formation, and the fluid penetrates the formation through the cracks. Sand grains, aluminum pellets, walnut shells, or similar materials (propping agents) are carried in suspension by the fluid into the cracks. When the pressure is released at the surface, the fracturing fluid returns to the well. The cracks partially close on the pellets, leaving channels for oil to flow around them to the well. See explosive fracturing, hydraulic fracturing.

A small attachment on the rod-transfer equipment that picks up the rods after they are unscrewed from the string and then transfers them to the rod hanger, or reverses the procedure when going into the hole. See rod-transfer equipment.

The action of pull out and subsequently running back into the hole a string of drill pipe or tubing. Making a round trip is also called tripping.

A type of packer used for open-hole work, with inflatable packing elements

The process in which reservoir fluids are caused to flow out of the reservoir rock and into a wellbore by natural energy. Gas drives depend on the fact that, as the reservoir is produced, pressure is reduced, allowing the gas to expand and provide the driving energy. Water-drive reservoirs depend on water pressure to force the hydrocarbons out of the reservoir and into the wellbore.

Steel pipe placed in an oil or gas well as drilling progresses to prevent the wall of the hole from caving in during drilling, to prevent seepage of fluids, and to provide a means of extracting petroleum if the well is productive.

A walled round hole or well in the hull of a drill ship (usually in the center) through which the drilling assembly and other assemblies pass while a well is being drilled, completed, or abandoned from the drill ship.

A reduction in the pressure of a fluid caused by its motion against an enclosed surface (such as a pipe). As the fluid moves through the pipe, friction between the fluid and the pipe wall and within the fluid itself creates a pressure loss. The faster the fluid moves, the greater are the losses.

The cementing operation that takes place immediately after the casing has been run into the hole. It provides a protective sheath around the casing, segregates the producing formation, and prevents the undesirable migration of fluids.

The cutting or boring element used in drilling oil and gas wells. This bit consists of a cutting element and a circulating element. The circulating element permits the passage of drilling fluid and utilized the hydraulic force of the fluid stream to improve drilling rates. In rotary drilling, several drill collars are joined to the bottom end of the drill pipe column, and the bit is attached to the end of the string of drill collars. Most bits used in rotary drilling are roller cone bits, but diamond bits are also used extensively.

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.

A short length of pipe (a nipple) installed on top of the blowout preventer. The top end of the nipple is flared, or belled, to guide drill tools into the hole and usually has side connections for the fill line and mud return line.

A trough or pipe that is placed between the surface connections at the wellbore and the shale shaker and through which drilling mud flows upon its return to the surface from the hole. Also called flow line.

To pull the drill stem out of the wellbore to change the bit, to change from a core barrel to the bit, to run electric logs, to prepare for a drill stem test, to run casing, and so on. Also called trip out.

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.

The recording of information derived from examination and analysis of formation cuttings made by the bit and of mud circulated out of the hole. A portion of the mud is diverted through a gas-detecting device. Cuttings brought up by the mud are examined under ultraviolet light to detect the presence of oil or gas. Mud logging is often carried out in a portable laboratory set up at the well.

The string of casing set in a well after the surface casing but before production casing is set. Keeps hole from caving and seals off troublesome formations. Also called protection casing.

A drilling method in which a hole is drilled by a rotating bit to which a downward force is applied. The bit is fastened to and rotated by the drill stem, which also provides a passageway through which the drilling fluid is circulated. Additional joints of drill pipe are added as drilling progresses.

A fishing tool that is attached to tubing or drill pipe and lowered over the outside wall of pipe or sucker rods lost or stuck in the wellbore. A friction device in the overshot, usually either a basket or as spiral grapple, firmly grips the pipe, allowing the fish to be pulled from the hole.

A special device that, when fitted in to the master bushing, transmits torque to the kelly and simultaneously permits vertical movement of the kelly to make hole. It may be shaped to fit the rotary opening or have pins for transmitting torque. Also called

The mud tank adjacent to the shake shaker, usually the first tank in to which mud flows after returning from the hole. Also called a shaker pit.

Two packers separated by a spacer of variable length. A straddle packer may be used to isolate sections of open hole to be treated or tested or to isolate certain areas of perforated casing from the rest of the perforated section.

Pressure at the top of a well when it is shut in.

2. pressure, volume, and temperature.

Pressure drop

See formation pressure

The derrickman's working platform. As pipe of tubing is run into or out of the hole, the derrickman must handle the top end of the pipe, which may be as high as 90 feet (27 m) in the derrick or mast. The monkeyboard provide a small platform to raise him to the proper height for handling the top of the pipe.

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.

A water-base mud in which water is the continuous phase and oil is the dispersed phase. The oil is spread out, or dispersed, in the water in small droplets, which are tightly emulsified so that they do not settle out. Because of its lubricating abilities, an oil-emulsion mud increases the drilling rate and ensures better hole conditions than other muds. Compare oil mud.

See extreme-pressure lubricant

1. to place pipe withdrawn from the hole on a pipe rack

A device used in fishing for drill pipe. If the upper end of the lost pipe is leaning against the side of the wellbore, the wall hook centers it in the hole so that it may be recovered with an overshot, which is run on the fishing string and attached to the wall hook.

An elastomer (seal) energized by pressure

Any law relating to the pressure, temperature, or volume of a gas.

2. the process of removing tubing from the well under pressure.

2. the process of putting tubing into a well under pressure.

Abbreviation: shut-in casing pressure

2. any pumping procedure in which fluid is pumped into the well against pressure.

Flexible coupling used in high-pressure lines.

Abbreviation: choke-line friction pressure.

To measure drill pipe or tubing as it is pulled out of the hole, usually to determine the depth of the well or the depth to which the pipe or tubing was run.

A surface device used in pressure control for slickline.

A pressure-multiplier-type well servicing mobile pump.

An unloader; provides a means to equalize tubing and annulus pressure.

To overcome pressure in a well by use of mud or water so that surface connections may be removed.

A means of cementing casing in a well so that the casing may, if necessary, be retrieved with minimum difficulty. A special mud, usually an oil mud, is placed in the well ahead of the cement after the casing has been set. Non-solidifying mud is used so that it does not bind or stick to the casing in the hole in the area above the cement. Since the mud does not gel for a long time, the casing can be cut above the cemented section and retrieved. Casing packs are used in wells of doubtful or limited production to permit reuse of valuable lengths of casing.

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.

3. trying to pump out a gas influx before the expansion of gas reduces pressure allowing the well to kick.

A sub in a DST string in which pressure and temperature recorders are placed for formation evaluation.

Abbreviation: shut-in drill pipe pressure, used in drilling reports.

(2) separating gas from that portion of associated and non-associated gas which liquefies at temperature and pressure conditions of the separator.

1. a device that mechanically or hydraulically forces pipe or tools into the well against pressure.

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.

A downhole tool with rough, sharp, extremely hard cutting surfaces for removing metal by grinding or cutting. Mills are run on drill pipe or tubing to grind up debris in the hole, remove stuck portions of drill stem or sections of casing for sidetracking, and ream out tight spots in the casing. They are also called junk mills, reaming mills, and so forth, depending on what use they have.

An injection well used for injecting fluids into an underground stratum to increase reservoir pressure.

Used to describe packers with one slip system for supporting weight and pressure from above only.

A well through which fluids are injected into an underground stratum to increase reservoir pressure and to displace oil.

3. a fractionation system that reduces the vapor pressure so that the resulting liquid is less volatile.

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.

A special mill that has a heavy tubular extension below it called a pilot or stinger. The pilot, smaller in diameter than the mill, is designed to go inside drill pipe or tubing that is lost in the hole. It guides the mill to the top of the pipe and centers it, thus preventing the mill from bypassing the pipe. Also called a piloted mill.

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.

A closed pressure vessel with a furnace to burn coal, oil, or gas, used to generate steam from water.

A device set in tubing, particular collars, to facilities the landing of pressure bombs (recorders).

(1) separating casinghead gas from produced crude oil and water at the temperature and pressure conditions of the separator; and

2. the increasing of external pressure on a diver's body caused by improper diving technique.

Application of hydraulic pressure to the reservoir formation to create fractures through which oil or gas may move to the well bore.

A fishing tool used to retrieve pipe lost in a well. The spear is lowered down the hole and into the lost pipe. When weight, torque, or both are applied to the string to which the spear is attached, the slips in the spear expand and tightly grip the inside of the wall of the lost pipe. Then the string, spear, and lost pipe are pulled to the surface.

A coring technique in which core samples are obtained from the hole wall in a zone that has already been drilled. A hollow bullet is fired into the formation wall to capture the core and then retrieved on a flexible steel cable. Core samples of this type usually range from 3/4 to 1-3/16 inches (20 to 30 millimeters) in diameter and from 3/4 to 4 inches (20 to 100 millimeters) in length. This method is especially useful in soft-rock areas.

Rubber seals that energize by pressure only, not mechanical force; plugs and wash tools

An opening or space within a rock or mass of rocks, usually small and often filled with some fluid (water, oil, gas, or all three). Compare vug.

A surface device used in slickline operations to keep the line lubricated and provide grease for pressure control

A surface device used in slickline operations to keep the line lubricated and provide grease for pressure control

Abbreviation: a generic term for pressure setting assembly; a tool that is used to set permanent tools on electric wireline, through explosive force.

Removing fluid from the tubing in a well, often by means of a swab, to lower the bottomhole pressure in the wellbore at the perforations and induce the well to flow.

2. a device fitted to the gauging hatch on a pressure tank that enables manual dipping and sampling without loss of vapor.

2. to pull formation fluids into a wellbore by raising the drill stem at a rate that reduces the hydrostatic pressure of the drilling mud below the bit.

A drillable tool configuration allowing the opening of formation pressure, during drillout, prior to cutting through the tools slips.

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.

1. a cementing operation in which cement is pumped behind the casing under high pressure to recement channeled areas or to block off an uncementred zone.

A rapid increase in n pressure downhole that occurs when the drill stem is lowered too fast or when the mud pump is brought up to speed after starting.

A short, threaded piece of pipe used to adapt parts of the drilling string that cannot otherwise be screwed together because of differences in thread size or design. A sub (i.e., a substitute) may also perform a special function. Lifting subs are used with drill collars to provide a shoulder to fit the drill pipe elevators; a kelly saver sub is placed between the drill pipe and the kelly to prevent excessive thread wear of the kelly and drill pipe threads, a bent sub is used when drilling a directional hole.

An accessory to a fishing tool, placed above it. if the tool cannot be disengaged from the fish, the safety joint permits easy disengagement of the string of pipe above the safety joint. Thus, part of the safety joint and the tool attached to the fish remain in the hole and become part of the fish.

2. the use of a high-pressure water stream to dislodge clingage and sediment from the bulkheads, bottoms, and internal structures of a vessel's cargo tanks.

The upward encroachment of water into a well caused by pressure drawdown from production.

A pipe through which pressure is bled, as from a pressurized tank, vessel, or other pipe.

To bleed pressure from casing of a dead well, then from tubing, then from casing, and so on so that the well will start to flow.

A bradenhead pack; no packer, very limited pack pressure capability.

A given point at a certain temperature and pressure at which no more solid material will dissolve in a liquid.

1. to drive oil from a reservoir into a well by injecting water under pressure into the reservoir formation. See waterflooding.

A sub with a ball seat run on top of a hydraulically set packer to set the packer.

Abbreviation: pounds per square inch absolute. See absolute pressure.

The pressure gradient (psi/ft) at which the formation accepts whole fluid from the wellbore.

A hanger used to lock instruments into seating nipple (pressure/temperature bombs, etc.).

A small plug that is run through a flow line by pressure to clean the line or test for obstructions (see pig).

The ratio of the actual volume of gas at a given temperature and pressure to the volume of gas when calculated by the ideal gas law.

2. in wireline, trying to pull out of the well faster than the wireline tools are being blown upwards by unexpected pressure.

Fracture induced by means of hydraulic or mechanical pressure exerted on the formation.

The ability of the formations to withstand applied pressure. Also called formation integrity.

Tubing pressure acting on the net piston area and causing a force to be exerted on a mandrel.

2. in reference to engines, a term used to describe the resistance to the flow of exhaust gas through the exhaust pipe.

An accessory or integral part of a packer used to limit the packer's upward movement under pressure.

Reduce pressure by letting oil or gas escape at a low rate.

A valve that will open automatically when pressure gets too high.

A paraffinic hydrocarbon that is a gas at ordinary atmospheric conditions but is easily liquefied under pressure. It is a constituent of liquefied petroleum gas.

The control valves, pressure gauges, and chokes assembled at the top of a well to control the flow of oil and gas after the well has been drilled and completed.

The amount of fluid that can be delivered through a permeable filter medium after being subjected to a set differential pressure for a set length of time.

To cause a gas or liquid to mingle slowly with another gas or liquid usually by pressure.

1. the high-pressure spraying of the crude oil cargo to dislodge or dissolve clingage and sediment from the walls, cross members, and lines in the compartments of a vessel during the unloading operation.

A cylindrical ring, usually vise-shaped, employed to back up (or assist) a sealing member against extrusion under temperature and pressure.

Weight per unit volume of drilling fluid usually expressed in pounds per gallon or pounds per cubic foot. See hydrostatic pressure.

An examination of reservoir fluid in a laboratory under various pressures, volumes, and temperatures to determine the characteristics and behavior of the fluid.

Lighter-duty well maintenance than hydraulic workover, employing small OD tubing capable of descending down the production string under well pressure

A device made up in the drill stem and lowered into the well to allow the casing and blowout preventers to b pressure-tested. The sealing device is cup-shaped and is therefore called a cup.

The closing and sealing component on a blowout preventer. One of three types--blind, pipe, or shear--may be installed in several preventers mounted in a stack on top of the wellbore. Blind rams, when closed, form a seal on a hole that has no drill pipe in it; pipe rams, when closed, seal around the pipe; shear rams cut through drill pipe and then form a seal.

A valve installed above the kelly that can be closed manually to protect the rotary hose from high pressure that may exist in the drill stem

A phenomenon in which a pressure concession occurs by suddenly stopping the flow of liquids in a closed container. Also called water hammer.

A method of severing steel pipe in a well by applying high-pressure jets of a very corrosive substance against the wall of the pipe. The resulting cut is very smooth.

A system of operating a certain oil and condensate reservoir in order to conduct some form of pressure maintenance, repressuring, waterflood, or other cooperative form to increase ultimate recovery.

A tool employing tripping devices that limit tool movement from pressure either above or below the tool

A hydrocarbon and water compound that is formed under reduced temperature and pressure in gathering, compression, and transmission facilities for gas. Hydrates often accumulate in troublesome amounts and impede fluid flow. They resemble snow or ice.

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. the pressure-sealing element of a stripper blowout preventer See stripper head.

Terminology used to describe a screen that, when packed off by gels, will give a pressure rise at the surface, thereby "telling" the tool operator that the gel has reached a certain location. Also called tattle-tale.

The topmost portion of a string of sucker rods. It is used for lifting fluid by the rod-pumping method. It has a uniform diameter and is smoothly polished to seal pressure effectively in the stuffing box attached to the top of the well.

A fluid-pressure test of the casing. Also called a cup test.

A series of hydraulic rams to restrain and pull tubing under well pressure, temporarily attached to the wellhead for workover.

Water put into an empty string of pipe in a wellbore to prevent the pipe from being crushed by pressure in the annulus.

Low-solids fluid or drilling mud used when a well is being completed. it is selected not only for its ability to control formation pressure, but also for the properties that minimize formation damage.

An electric or hydraulic pump on an accumulator that pumps hydraulic fluid under high pressure to the blowout preventers so that they may be closed or opened.

1. the process of lowering the drill stem into the wellbore when the well is shut in on a kick and when the weight of the drill stem is sufficient to overcome the force of well pressure.

See hydrostatic pressure