| 摘要 |
A jet shoe (10) is connected to the lowermost end of a pipe (31) to be placed in a subsea formation. The jet shoe comprises a cylindrical housing (10a) in which is arranged an inner tubular receptacle (11), a check valve (18) permitting downward flow but preventing upward flow through the valve and jet tubes (15) extending from receptacle (11) through the lower end of jet shoe (10). Receptacle (10), valve (18) and tubes (15) are cemented in housing (10a). Tubes (15) contain nozzles (16) for jetting fluid to erode formation ahead of shoe (10) A stinger (27) arranged on the lower end of a smaller diameter pipe (25) extends into and seals in receptacle (11). A closure member (35) on smaller pipe (25) releasably closes off the upper end of larger pipe (31). The smaller pipe (25) and the attached larger pipe (31), together with a permanent guide base (45) connected to the upper end of larger pipe (31), are lowered to the ocean floor. While jetting fluid through smaller pipe (25) and out shoe (10), the formation ahead of the shoe (10) is eroded until larger pipe (31) reaches a predetermined depth. Cement slurry (50) is then pumped downwardly through smaller pipe (25) and through jet shoe (10) to cement larger pipe (31) in the subsea formation. If desired, a pressure measuring means (40, 42) may be provided to determine whether any leaks have occurred in the drill pipe. The invention has particular application in locations where the subsea formations are unstable and in locations where it is advantageous to eliminate running of a temporary guide base in offshore operations. |
