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.

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

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.

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

Homemade; something done on a shoestring basis.

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.

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.

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).

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that is carried in suspension by the fracturing fluid and that serves to keep the cracks open when fracturing fluid is withdrawn after a fracture treatment.

To begin drilling; to start the hole.

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.

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