Rotary Drilling Unit I Lesson 3: Drill String And Drill Collars

In rotary drilling, a crew rotates a bit that drills a hole through the earth in search of oil or gas. The crew attaches the bit to a hollow length of pipe that serves two purpose: it provides the weight to make the bit dig into the earth's formations, and it provides a passageway to circulate a fluid drilling mud to the bit as it rotates.

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