| 摘要 |
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 an apparatus for providing a modified cutting action of the bit in a predetermined portion of the hole, a stabilizer, and a flexible member interposed between the bit and the 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 aluminum 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.
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