Oil & Gas Glossary 1.0

A secondary-cementing operation in which a plug of cement is positioned at a specific point in the well and allowed to set.

A rubber plug used in primary cementing operations to displace cement slurry from the casing into the borehole annulus.

See cementing head.

A rubber-bodied, plastic- or aluminum-cored device used to separate cement and drilling fluid as they are being pumped down the inside of the casing during cementing operations. A wiper plug also removes drilling mud that adheres to the inside of the casing.

To shut off lower formation in a well bore.

The application of a liquid slurry of cement and water to various points inside or outside the casing. See primary cementing, secondary cementing.

A squeeze cementing method in which a packer is set to form a seal between the working string (the pipe down which cement is pumped) and the casing. Another packer or a cement plug is set below the point to be squeeze-cemented. By setting packers, the squeeze point is isolated from the rest of the well. See packer, squeeze cementing.

A portion of cement placed at some point in the wellbore to seal it. See cementing.

An accessory attached to the top of the casing to facilitate cementing of the casing. It has passages for cement slurry and retain chambers for cementing wiper plugs.

A temporary plug set of a PSA, landed in a production packer to convert it to a bridge plug.

To perform one or more of a variety of remedial operations on a producing oil well to try to increase production. Examples of workover opera6tions are deepening, plugging back, pulling and resetting liners, squeeze cementing, and so on.

A tool set temporarily in the casing or well to prevent the passage of cement, thereby forcing it to follow another designated path. It is used in squeeze cementing and other remedial cementing jobs.

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

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 forcing of cement slurry by pressure to specified points in a well to cause seals at the points of squeeze. It is a secondary cementing method that is used to isolate a producing formation, seal off water, repair casing leaks, and so forth.

A downhole tool, composed primarily of slips, a plug mandrel, and a rubber sealing element, that is run and set in casing to isolate a lower zone while an upper section is being tested or cemented.

See gunk plug

To displace the wellbore fluid back to the surface; to displace tubing volume back to the pit.

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

To pass from one point throughout a system and back to the starting point. For example, drilling fluid is circulated out of the suction pit, down the drill pipe and drill collars, out the bit, up the annulus, and back to the pits while drilling proceeds.

A large, specially designed, self-propelled workover rig that a person drives directly to the well site. Power from a carrier rig's hoist engine or engines also propels the rig on the road. While a carrier rig is primarily intended to perform workovers, it can also be used to drill relatively shallow wells. A carrier rig may be a back-in type or a drive-in type. See back-in unit, drive-in unit.

A generic term used to describe a retrievable service squeeze tool; used in remedial cementing.

Abbreviation: plug and abandon

To unscrew.

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.

1. forcing gas back into a formation by pumping into the annulus from the surface.

A sliding-sleeve ported casing section used in stage cementing.

A generic term, originally a trademark name, used to describe a stage tool, used in selective zone primary cementing.

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

A tube placed around the retrieving neck of a retrievable bridge plug to "catch" debris.

1. to cease efforts to produce oil or gas from a well, and to plug a depleted formation and salvage all material and equipment.

A substance added to cement to prolong the setting time so that the cement can be pumped into place. Retarders are used for cementing in high-temperature formation

The string of drill pipe tubing suspended in a well to which is attached a special tool or device that is used to carry out a certain task, as squeeze cementing or fishing.

The string of drill pipe or tubing suspended in a well to which is attached a special tool or device that is used to carry out a certain task, such as squeeze cementing or fishing.

A tool used to mill over permanent bridge plugs/cement retainers while retrieving the milled-out debris

A bull plug or blind flange at the end of a tee to prevent erosion at a point where change in flow direction occurs.

A method of squeeze cementing in which cement is pumped in and the pumps are stopped for a few minutes. Pumping is started and stopped until the desired pressure is obtained.

A retrievable tool used to suspend drilling temporarily during a storm offshore.

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

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

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

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.

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

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

To close off, such as with a blank flange or bull plug.

To plug open perforations by using ball sealers.

Movement of drilling fluid from mud pits, down drill stem, up annulus, and back to mud pits.

A reservoir formation in which fluid or plastic masses of rock material originated at unknown depths and pierced or lifted the overlying sedimentary strata.

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

A clamp used to hold the rod string in pumping position when the well is in the final stages of being put back on the pump.

To hold one section of an object such as pipe while another section is being screwed into or out of it.

The person who holds one length of pipe while another length is being screwed into or out of it.

A slurry in crude or diesel oil containing any of the following materials or combinations: bentonite, cement, attapulgite, and guar gum (never with cement). Used primarily in combating lost circulation.

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

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.

A settled volume of barite particles from a barite slurry placed in the wellbore, usually to seal off a pressured zone.

The act of pulling tubing out of and running it back into a well.

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

The process of pumping mud downward to the bit and back up tot he surface in a drilling or workover operation. See normal circulation, reverse circulation.

A portable servicing or workover rig that is self-propelled, using the hoisting engines for motive power. Because the driver's cab is mounted on the end opposite the mast support, the unit must be backed up to the wellhead. See carrier rig.

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

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.

See back-pressure

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.

To place stands of drill pipe and drill collars in a vertical position to one side of the rotary table in the derrick or mast of a drilling or workover rig. Compare lay down pipe.

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

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 wheel-shaped wrench that is attached to the sucker rod string at the surface and is manually turned to unscrew the string to allow it to be pulled from the well.

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

A tool used to open or close a downhole valve; a tool used to set or release a downhole tool, such as a retrievable bridge plug.

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.

See valve

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 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

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.

Any valve installed in the drill stem to prevent a blowout through the stem. Mud can be pumped in but flow back up the stem is prevented. Also called an internal blowout preventer.

The liquid circulated through the wellbore during rotary drilling and workover operations. In addition to its function of bringing cuttings to the surface, drilling mud cools and lubricates the bit and drill stem, protects against blowouts by holding back subsurface pressures, and deposits a mud cake on the wall of the borehole to prevent loss of fluids to the formation. See drilling fluid.

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.

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 slurry of portland cement and water and sometimes one or more additives that affect either the density of the mixture or its setting time. The portland cement used may be high early strength common (standard), or slow setting. Additives include accelerators (such as calcium chloride), retarders (such as gypsum), weighting materials (such as barium sulfate), lightweight additives (such as bentonite), or a variety of lost circulation materials (such as mica flakes).

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.

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.

A dome that is caused by an intrusion of rock salt into overlying sediments. A piercement salt dome is one that has been pushed up so that it penetrates the overlying sediments, leaving them truncated. The formations above the salt plug are usually arched so that they dip in all directions away from the center of the dome, thus frequently forming traps for petroleum accumulations.

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.

The state in fluid dynamics of a fluid in motion is determined by the type of fluid (e.g., Newtonian, plastic, pseudoplastic, dilatant); the properties of the fluid such as viscosity and density; the geometry of the system; and the velocity. Thus, under a given set of conditions and fluid properties, the fluid flow can be described as plug flow, laminar (called also Newtonian, streamline, parallel, or viscous) flow, or turbulent flow.

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.

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 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 pump consisting of a piston that moves back and forth or up and down in a cylinder. The cylinder is equipped with inlet (suction) and outlet (discharge) valves. On the intake stroke, the suction valves are opened, and fluid is drawn into the cylinder. On the discharge stroke, the suction valves close, the discharge valves open, and fluid is forced out of the cylinder.

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 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.