| 摘要 |
Apparatus and methods operate to seal off a column of effluents standing in a borehole annulus from a drill bit assembly during earth drilling operations. A seal assembly, sections of drill pipe, and tubular casing members are assembled into a fluid pressure-restraining drilling tool. The drilling tool is inserted into a drill string above the drill bit. The seal assembly tracks with the drill string, traveling along the borehole wall to maintain an annular seal at a substantially constant position above the drill bit as drilling operations progress. Pressures produced by the column of effluents are exerted at the upper portion of the seal as the effluent column is prevented from reaching the drill bit.
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