| 摘要 |
A well drilling bit (1) comprising a bit body (8) attachable to a tubular drill string (3), which bit body (8) is internally provided with a passagewa y (18) providing fluid communication, when the drill string (3) is attached to the bit body (8), between the interior (19) of the drill string and the exterior (20) of the bit body (8); a closure element (25) for selectively closing the passageway (18); and one or more chip-making elements (11,12,13) , wherein the chip-making elements (11,12,13) comprise one or more roller- con es (11,12,13), wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position to an opening position, and wherein the closure element includes at least one of the roller-cones.</ SDOAB>
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