| 摘要 |
<p>Described herein is a turbine-drill bit assembly (600) in which the gap between the turbine and the drill bit is minimised and overall assembly is substantially shorter. The assembly (600) comprises a box connection turbine (610) connected to a pin connection drill bit (500). The turbine (610) has a turbine body (640, 650, 650a, 650b) around a turbine shaft (630), the turbine body (640, 650, 650a, 650b) having a turbine stabiliser (650, 650a, 650b). The drill bit (500) has a bit gauge or a bit sleeve (530) around a bit shank (520), an end (655) of the turbine stabiliser (650) nearest the drill bit (500) being spaced a first maximum distance (A) from an end (535) of the bit gauge or bit sleeve (530). In addition, a shouldering interface (560) is formed at respective abutment shouldering surfaces (635, 525) of the turbine shaft (630) and bit shank (520) when the drill bit (500) is attached to the turbine shaft (630), the interface (560) being spaced a second maximum distance (B) from an end (535) of the bit gauge or bit sleeve (530). The advantage of these limited distances reduces the annular volume in which mud and rock debris can build up thereby reducing erosion and wear, !n addition, a more rigid assembly is provided which is less susceptible to vibrations. This reduces the risk of sticking of the turbine-drill bit assembly in the wellbore and provides better directional control.</p> |
