| 摘要 |
PCT No. PCT/GB96/00556 Sec. 371 Date Sep. 16, 1998 Sec. 102(e) Date Sep. 16, 1998 PCT Filed Mar. 11, 1996 PCT Pub. No. WO96/28635 PCT Pub. Date Sep. 19, 1996A casing shoe (30) for use in guiding a casing into a wellbore comprises a generally cylindrical body (2) having a box portion (34) at its rearward end for connection to a casing string and having a generally rounded nose portion (36) at its forward end. The forward end of the shoe includes cutting structures (42, 44) in the form of raised flutes extending along the sides of the cylindrical body and on the nose portion. The flutes may be provided with cutting elements such as polycrystalline diamond compact elements (48) at least at the forward ends of the flutes (42) extending along the cylindrical body. These flutes may also be configured to serve as stabilising pads, and additional stabilising pads (38) may also be provided. The nose portion may include fluid passages (50). The shoe may be adapted to be capable of being drilled through, such as by forming the nose portion from a drillable material. The provision of cutting structures on the casing shoe allows the tool to remove or negotiate obstacles which would prevent the passage of conventional casing shoes. The trailing ends of the various flutes may be provided with abrasive material to provide a back-reaming capability. The nose portion may also be eccentrically shaped to assist in negotiating obstacles.
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