After the data are analyzed, the results are displayed in three-dimensional color. Yet despite all this technology, wells are not always successful. As the saying goes, the only way to discover oil is with a drill. A heavy iron bit, tipped with steel, was suspended by a cable from a drilling derrick and repeatedly smashed into the ground. Although laborious and slow, this method was still used as late as the 1960s, for shallow wells in rocky areas.
Rotary drills are more common today.
Although some rotary drills were in operation for water wells as early as 1823, the method did not become widespread in the U.S. until 1900. By 1930s it was the dominant form of drilling, used extensively in the deep wells of Oklahoma, Texas and California. In a rotary drill, a sharp tip of diamonds embedded in hardened steel bites into the ground, connected to motors on the surface by a long string of drilling pipes. The pipes, about 30 feet long each, are screwed together into strings as long as 24,000 feet, weighing up to 100 tons. Muddy water is pumped down through the drilling pipes to carry the chips of rock cut by the drill back to the surface.