ASSOCIATED GAS

Natural gas produced with crude oil from the same reservoir.

BARREL

Unit of measure for oil and petroleum products that is equivalent to 42 U.S. gallo

BLOWOUT

The uncontrolled flow of gas, oil or other fluids from a well

BLOWOUT PREVENTER (BOP)

The equipment installed at the wellhead to control pressures in the annular space between the casing and drill pipe or tubing during drilling, completion, and workover operations.

BRITISH THERMAL UNIT (BTU)

A measure of the heating value of a fuel.

CASING

Metal pipe inserted into a wellbore and cemented in place to protect both subsurface formations (such as groundwater) and the wellbore. A surface casing is set first to protect groundwater.