Oil & Gas Terms of The Day


Makeup cathead

A device that is attached to the shaft of the drawworks and used as a power source for screwing together joints of pipe. It is usually located on the driller’s side of the drawworks. Also called spinning cathead. See cathead.

Blowout preventer operating and control system

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

Igneous rock

A rock mass formed by the solidification of material poured (when molten) into the earth’s crust or onto its surface. Granite is an igneous rock.

Macaroni rig

A workover rig, usually lightweight, that is specially built to run a string of 3/4 inch or 1-inch tubing. See macaroni string.

Poor boy

Homemade; something done on a shoestring basis.

External cutter

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.

Gel strength

A measure of the ability of a colloidal dispersion to develop and retain a gel form, based on its resistance to shear. The gel, or shear, strength of a drilling mud determines its ability to hold solids in suspension. Sometimes bentonite and other colloidal clays are added to drilling fluid to increase its gel strength.

Pressure gauge

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).

Propping agent

A granular substance (sand grains, aluminum pellets, or other material) that is carried in suspension by the fracturing fluid and that serves to keep the cracks open when fracturing fluid is withdrawn after a fracture treatment.

Spud in

To begin drilling; to start the hole.

Drill stem

All members in the assembly used for rotary drilling from the swivel to the bit, including the kelly, drill pipe and tool joints, drill collars, stabilizers, and various specialty items. Compare drill string.

Sour corrosion

Embrittlement and subsequent wearing away of metal caused by contact of the metal with hydrogen sulfide.