Texas oil well workers, circa 1955. An oil

well is a general term for any boring through

the earth's surface that is designed to find

and acquire petroleum oil hydrocarbons.

Usually some natural gas is produced along

with the oil. A well that is designed to

produce mainly or only gas may be termed a

gas well. The well is created by drilling a

hole 5 to 50 inches (127.0 mm to 914.4 mm) in

diameter into the earth with a drilling rig

that rotates a drill string with a bit

attached. After the hole is drilled, sections

of steel pipe (casing), slightly smaller in

diameter than the borehole, are placed in the

hole. Cement may be placed between the

outside of the casing and the borehole.