| 摘要 |
<p>A rotary drill bit for drilling a well bore comprising a bit body (3) adapted to be detachably secured to a drill string and receive drilling fluid under pressure therefrom and having a plurality of depending legs (7) and a nozzle system (15) for exit of drilling fluid from the bit body. The drill bit further comprises a plurality of roller cutters (9), each cutter having a generallly conical roller cutter body (11) rotatably mounted on one of the legs (7) and a plurality of cutting elements (13) on the cutter body (11). The nozzle system directs a plurality of streams (S) of drilling fluid from the bit body (3), each stream (S) being so directed as to flow generally toward the cutter body (11) of a roller cutter (9), with the stream (S) impinging at least one cutting element (13) on the roller cutter body (11), and thereafter impinging the well bore bottom (T) at least in part at a generally pie shaped portion of the bottom which is within the vertical projection of the roller cutter (9) on the well bore bottom and forward, with respect to the direction of rotation of the drill bit, of the points of engagement of the cutting elements (13) of this latter roller cutter with the well bore bottom for improved cleaning action.</p> |
