Drill stems must be designed to transfer drilling torque for combined lengths that often exceed several miles down into the , and also must be able to resist pressure differentials between inside and outside (or vice versa), and have sufficient strength to suspend the total weight of deeper components. For deep wells this requires tempered steel tubes that are expensive, and owners spend considerable efforts to reuse them after finishing a well.
[pdf] This casing string provides initial hole support close to the surface and generally varies in length from about 30 to 300 feet. The casing may be driven or hole drilled. The casing may be cemented if it is nece.
[pdf] Keep hands off the stump of pipe in the rotary or mouse hole. Only place hands on tong handles. Keep hands off of the tong latch except to open the tongs. Keep an eye on swinging tongs at all times. Stand clear of the spinning chain. Never put your hand on top of the drill pipe or collar box at any time.
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