| 摘要 |
<p>The present invention provides a bottom hole assembly (BHA) for connection to a drillstring for use in directing the path of a drill bit while rotary drilling, the BHA comprising a drill bit arrangement (1), means (2) for providing a modified cutting action of the bit in a predetermined portion of the hole during rotation according to according to the rotary position of the bit in the hole, and a stabilizer (3), the BHA being characterised in that a flexible member (2) is interposed between the bit and said stabilizer. By "flexible" member is meant a member made from a material having a lower Young's modulus than steel and/or a member with a smaller wall thickness than the remainder of the BHA. In the case where the BHA is formed from steel pipe, a flexible member might be provided by an aluminium drill collar or a composite material drill collar. Alternatively or additionally, the wall thickness of the material from which the collar is formed can be made less than the remainder of the BHA. <IMAGE></p> |
