Oil & Gas Glossary 1.0

Abbreviation: perforating depth control log

A logging device used to determine accurately the depth of a well; the log measures and records the depth of each casing collar, or coupling, in a well. Since the length of each joint of casing is written down, along with the number of joints of casing that were put into the well, knowing the number and depth of the collars allows an accurate measure of well depth

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.

The maximum depth reached in a well.

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.

A sub with a glass blockage in the bore, used to isolate a surge chamber in gravel packing or perforation cleaning operations.

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.

1. a pipe connection around a valve or other control mechanism that is installed to permit passage of fluid through the line while adjustments or repairs are being made on the control.

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 manifold system of valves, usually situated at the power source, which may be operated manually (or by remote control) to direct pressurized fluid to closing devices at wellhead.

A system of controls, convenient to the driller, which can be used selectively to actuate valves at the master control panel.

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 well drilled near and deflected into a well that is out of control, making it possible to bring the wild well under control. See wild well.

A station containing equipment to control and regulate operations in the field.

The section of a drawworks drum grooved for angle control and in which the wire rope crosses over to start a new wrap. Also called an angle-control section.

Abbreviation: total depth

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).

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

To obtain an accurate measurement of the depth reached in a well by measuring the drill pipe or tubing as it is run into the well.

A variation of squeeze cementing for wells with two producing zones in which (1) the upper fluid sand is perforated; (2) tubing is run with a packer, and the packer is set between the two perforated intervals; (3) water is circulated between the two zones to remove as much mud as possible from the channel; (4) cement is pumped through the channel and circulated; (5) the packer is released and picked up above the upper perforation, a low squeeze pressure is applied, and the excess cement is circulated out. The process is applicable where there is communication behind the pipe between the two producing zones because of channeling of the primary cement or where there is essentially no cement in the annulus.

A tubular device that, when lowered to a selected depth within a well, fires bullets through the casing to provide holes through which the formation fluids may enter the wellbore.

A device fitted with shaped charges or bullets that is lowered to the desired depth in a well and fired to create penetrating holes in casing, cement, and formation.

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

To run and cement casing at a certain depth in the wellbore. Sometimes called set pipe.

(2) to control the quality of the natural gas to be marketed.

A record of certain electrical characteristics (such as resistivity and conductivity) of formations traversed by the borehole. It is made to identify the formations, determine the nature and amount of fluids they contain, and estimate their depth.

A surface device used in pressure control for slickline.

A record showing variations in wellbore diameter by depth, indicating undue enlargement due to caving in, washing, or other causes. The caliper log also reveals corrosion, scaling, or pitting inside tubular goods.

The foundation on which the derrick or mast and usually the drawworks sit. It contains space for storage and well-control equipment.

A well that has blown out of control and from which oil, water, or gas is escaping with great force to the surface. Also called a gusher.

The normal pressure divided by true vertical depth.

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

The assembly of well-control equipment including preventers, spools, valves, and nipples connected to the top of the wellhead.

A synthetic high-molecular-weight polymer of acrylonitrile used primarily as a fluid loss control agent

Part of a computer system that contains manual controls--switches and devices to start, stop, measure, monitor or signal what is taking place.

A string of tubing used to produce the well, providing well control and energy conservation.

A plan or procedure, with respect to depth, for the type and properties of drilling fluid to be used in drilling a well. Some factors that influence the mud program are the casing program and such formation characteristics as type, competence, solubility, temperature, and pressure.

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

A device with a restricted opening placed in the lower end of the tubing to control the rate of flow. See choke.

To control a blowout by placing a very strong valve on the wellhead. See blowout.

A system whereby the end devices in the field (switches, valves, gauges, alarms, etc.) are controlled by a program placed in the computer.

A flow-control device employing a ball with a rotating mechanism to open or close the tubing medium.

Well-control fluid that has been reduced in density or unit weight as a result of entrainment of less-dense formation fluids or air

In well-control operations, closing the BOP's with the choke and HCR, or fail-safe, valves open. Compare hard shut-in.

A small hydraulic line used to communicate fluid from the surface to a downhole tool, such as a subsurface safety valve.

An organization whose function is to establish standards and recommended practices for the field of corrosion control.

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.

To obtain cuttings for geological information as formations are penetrated by the bit. The samples are obtained from drilling fluid as it emerges from the wellbore or, in cable-tool drilling, from the bailer. Cuttings are carefully washed until they are free of foreign matter, dried, and labeled to indicate the depth at which they were obtained.

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.

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.

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

An extension from the blowout preventer assembly used to direct control the flow of well fluids from the annulus to the choke.

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.

Materials added to the mud in varying amounts to control or prevent lost circulation. Classified as fiber, flake, or granular.

Materials added to the mud in varying amounts to control or prevent lost circulation. Classified as fiber, flake, or granular.

An extension of a retrievable tool, i.e., a retrievable bridge plug, used to set and release the tool.

1. a large valve located on the Christmas tree and used to control the flow of oil and gas from a well. Also called master gate. 2. the blind or blank rams of a blowout preventer (obsolete).

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.

A permanent packer, drillable in nature, capable of withstanding extreme working pressures, for remedial work. It has a positive flow-control valve built in.

The assembly of pumps, valves, lines, accumulators, and other items necessary to open and close the blowout preventer equipment. Also called closing unit.

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.

Controls, usually located near the driller's position on the rig floor, that are manipulated to open and close the blowout preventers. See blowout preventer.

A screen joint placed opposite perforations in sand control

A tool composed of a mandrel on which are mounted several heavy-duty rollers with eccentric roll surfaces. It is used to restore buckled, collapsed, or dented casing in a well to normal diameter and roundness. Made up on tubing or drill pipe and run into the well to the depth of the deformed casing, the tool is rotated slowly, allowing the rollers to contact all sides of the casing and restore it to roughly its original condition.

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.

2. to dose the blowout preventers on a well to control a kick. The blowout preventers close off the annulus so that pressure from below cannot flow to the surface.

Any method by which large amounts of sand in a sandy formation are prevented from entering the wellbore. Sand in the wellbore can cause plugging and premature wear of well equipment. See gravel pack, sand consolidation, screen liner.

A set of controls, usually placed on the rig floor, that is manipulated to control the amount of drilling fluid being circulated through the choke manifold. This procedure is necessary when a kick is being circulated out of a well. See choke manifold.

An arrangement of piping and special valves, called chokes. In drilling, mud is circulated through a choke manifold when the blowout preventers are closed. In well testing, a choke manifold attached to the wellhead allows flow and pressure control for test components downstream.

A method of killing a well in which the mud level in the pits is held constant while the choke size is reduced and the pump speed slowed. It is not effective, and therefore, is not recommended, because casing pressure increases to the point at which the formation fractures or casing ruptures, and control of the well is lost.

A part of the brake mechanism consisting of a flexible steel band lined with a material that grips a drum when tightened. On a drilling rig, the brake band acts on the flanges of the drawworks drum to control the lowering of the traveling block and its load of drill pipe, casing, or tubing.

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 device used to control the rate of flow in a line to open or shut off a line completely, or to serve as an automatic or semiautomatic safety device. Those used extensively include the check valve, gate valve, globe valve, needle valve, plug valve, and pressure relief valve.

A globe valve that contains a sharp, pointed, needle-like plug that is driven into and out of a cone-shaped seat to control accurately a relatively small rate of fluid flow. In a fuel injector, the fuel pressure forces the needle valve off its seat to allow injection.

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.

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.

An exploration method in which strong low-frequency sound waves are generated on the surface or in the water to find subsurface rock structures that may contain hydrocarbons. The sound waves travel through the layers of the earth's crust; however, at formation boundaries some of the waves are reflected back to the surface where sensitive detectors pick them up. Reflections from shallow formations arrive at the surface sooner than reflections from deep formations, and since the reflections are recorded, a record of the depth and configuration of the various formations can be generated. Interpretation of the record can reveal possible hydrocarbon-bearing formations.

A floating offshore drilling unit that has pontoons and columns that when flooded cause the unit to submerge in the water to a predetermined depth. Living quarters, storage space, and so forth a reassembled on the deck. Semisubmersible rigs are either self-propelled or towed to a drilling site and either anchored or dynamically positioned over the site, or both. In shallow water, some semisubmersibles can be ballasted to rest on the seabed. Semisubmersibles are more stable than drill ships and ship-shaped barges and are used extensively to drill wildcat wells in rough waters such as the North Sea. Two types of semisubmersible rigs are the bottle-type semisubmersible and the column-stabilized semisubmersible. See floating offshore drilling rig.

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.

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.