| 摘要 |
<p>A rotary drill bit comprises a bit body (10) having a leading face (11) and a gauge region (12), a plurality of blades (13) extending across the leading face (11) of the bit body (10), a plurality of cutting elements (8) mounted along each blade, an exit channel (18) in the gauge region (12) of the bit body (10) between each pair of adjacent blades (13), a plurality of nozzles (19a,19b,19c,19d) in the leading face (11) of the bit, each nozzle having a central axis (20) which also forms the central axis of the jet of drilling fluid emerging from the nozzle, and a passage (6) in the bit body (10) for supplying drilling fluid to said openings (19a-19d). At least one nozzle is located between each pair of adjacent blades (13), and the nozzles are inclined at different angles, or are otherwise differently located, so that, in use, the central axes of nozzles between different pairs of adjacent blades (13) intersect the surface of the formation (21) being drilled at different distances from the axis of rotation of the bit, so that the jets of drilling fluid emerging from the nozzles, between them, sweep over the whole of the surface of the formation as the bit rotates.</p> |
