The basic unit for measuring oil. A barrel is equal to 42 U.S. gallons.

A drilling tool that cuts the hole. Bits are designed on two basic and different principles. The cable tool bit moves up and down to pulverize. The rotary bit revolves to grind.

A heavy casinghead control, filled with special gates or rams, which can be closed around the drill pipe, or which completely closes the top of the casing.

British Thermal Unit, a generalized measure of heating value, also used to compare energy potential in different types of fuels.

Heavy steel pipe used to seal off fluids from the hole or to keep the hole from caving in.

Gas produced with oil in oil wells. The gas is taken from the well through the casinghead at the top of the well.

A refining process for breaking down large, complex hydrocarbon molecules into smaller ones. A catalyst is used to accelerate the chemical reactions in the cracking process.

The assembly of valves, pipes and fittings used to control the flow of oil and gas from the casinghead.

Liquid hydrocarbons recovered by surface separators from natural gas. It is also referred to as natural gasoline and distillate.

Liquid petroleum as it comes out of the ground. Crude oil varies radically in its properties, such as specific gravity and viscosity.