| 摘要 |
Retrieving a down hole tool at a lower end of a string of casing can be performed with drill pipe during a casing-while-drilling operation. The operator suspends the casing on a landing sub landed in a drilling rig floor opening. A string of drill pipe is lowered into the casing while the casing is suspended for engaging and retrieving the down hole tool. A spillage preventer in the landing sub prevents spillage of drilling fluid as the drill pipe is being retrieved. When circulation is desired, the operator secures a circulation tool to an upper end of the drill pipe, then lowers the drill pipe and the circulation tool to close off an upper end of an inner annulus between the drill pipe and the casing. A connection between the circulation tool and the landing sub allows the operator to reciprocate the casing.
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