| The rotary drilling rig uses a series of rotating pipes, called the drill string, to tap into oil reservoirs. The drill string is supported by a derrick, and turned by the rotary table on its floor. Circulating, mudlike fluid driven by a pump removes cuttings as the teeth of the drill bit dig into the rock around the reservoir. Reservoirs occur in many places. They form as a result of intense pressure on top of layers of dead marine and land organisms mixed with sand or silt. This reservoir abuts a salt dome, which has trapped a layer of oil and natural gas between itself and nonporous rock. Because they have no place to expand, the gas and crude oil are under high pressure and will tend to rush explosively out the channel opened by the drill rig. |
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