Petroleum: Rotary Drilling (OG-11)
A steel bit is attached to the end of the drill pipe. The bit and pipe pass through a rotary turntable on the derrick floor. As the power unit turns the table, the bit bores a hole. New lengths of pipe are added as the hole deepens.

Mud of water, clays, weighting agents and chemicals is pumped down the hollow pipe and is forced to the surface between the pipe and the walls of the hole. It lubricates and cools the bit and flushes cuttings to the surface. It also prevents caving and helps oil, gas or water until the hole is ready to test. When the bit becomes dull, stands of pipe are stacked in the derrick, the bit is changed, and the string of tools is returned to the hole. The bit may drill only a few feet into hard rock before it dulls again. Rotary drilling was first used about 1893, but it did not dominate Gulf Coast drilling until after 1901. Now more than 85 percent of all wells are drilled by this method, and more than 4,000 rigs operate in the United States alone.

Our Hoosier State Beneath Us: Oil and Gas