Oil & Gas Glossary 1.0

A specialized fixture on a downhole tool that will allow the tool to be fished out after it's used downhole. See fish.

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.

The person (usually a service company employee) in charge of directing fishing operations.

An accessory attached o the top of the drill pipe or tubing to form a connection with the mud system to permit circulation of the drilling mud. In some cases, it is also a rotating head.

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.

See fishing string.

A hydraulically operated tool that is run in above the fishing tool and anchored to the casing by slips. It exerts a strong upward pull on the fish by hydraulic power derived from fluid that is pumped down the fishing string.

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.

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.

See cementing head.

Commonly called casinghead gas; gas that is produced with oil or from the casing head of an oil well.

The procedure of recovering lost or stuck equipment in the wellbore. See fish.

A fishing tool used to recover a pared string of sucker rods from a well.

A fishing accessory run above a bit or a mill to recover small, nondrillable pieces of metal or junk.

The driller or head well puller in charge of operations on a well servicing rig that is used to pull sucker rods or tubing

2. to remove the settlings and cavings that are plugged inside a hollow fish (such as drill pipe) during a fishing operation.

A tool that goes inside pipe lost in a well to provide a firm grip and permit recovery of the fish. Sometimes used in place of a spear.

A blowout prevention device consisting of a gland and packing arrangement bolted to the wellhead. It is often used to seal the annular space between tubing and casing.

Distance between well head and point to which fluid rises in the well.

A powerful permanent magnet designed to recover metallic objects lost in a well.

A device placed on a piece of equipment that is lowered into a wellbore so that the equipment may be retrieved by wire line.

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 tool designed to recover equipment lost in a well.

2. To remove the settlings and cavings that are plugged inside a hollow fish (such as drill pipe) during a fishing operation.

A percussion tool run on a fishing string to jar downward or upward on a stuck fish to knock it free. The bumper sub body moves up and down on a mandrel.

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.

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.

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 complete break in pipe caused by metal fatigue. v: to break something in two or to break apart, such as the head of a bolt or the drill stem.

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

An arrangement of slips and packing rings used to suspend tubing from a tubing head.

2. a large pipe connected to a process tank to provide a statis head that can absorb surges of fluid from the process tank.

See hydrostatic pressure

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

A flanged fitting that supports the tubing string, seals off pressure between the casing and the outside of the tubing, and provides a connection that supports the Christmas tree.

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.

The equipment installed at the surface of the wellbore. A wellhead includes such equipment as the casinghead and tubing head. adj: pertaining to the wellhead (e.g., wellhead pressure).

A worker on an offshore rig who handles the equipment and supplies that are sent to the rig form the shore base. The head roustabout is very often the crane operator. a worker who assists the foreman in the general work around a producing oilwell, usually on the property of the oil company. A helper on a well servicing unit.

2. a stripper head.

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

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 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.

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 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 device run on wireline into the wellbore and inside the fishing string and fish to locate the area where a fish is stuck. When the drill string is pulled and turned, the electromagnetic fields of free pipe and stuck pipe differ. The free-point indicator is able to distinguish these differences, which are registered on a metering device at the surface.

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.

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.