Patent GB-1245740-A (GB)
Title: Equipment for a well penetrating a formation located below a body of water
Inventor: EEK WOUTER HUGO VAN
IPC: E21B7/124
Filed: 1970-06-17
Abstract: 1,245,740. Wells etc; boring earth &c. SHELL INTERNATIONALE RESEARCH MAATSOIAPPIJ N.V. 17 June, 1970, No. 29424/70. Heading E1F. In an underwater well comprising a pedestal conductor 17 carrying a wellhead 16 and coupled to a conductor 5 cemented in the sea bed, a production tubing 33 supported by the wellhead communicates with a production string 30 supported by the conductor. The pedestal conductor has a buoyancy member 19, or buoyancy members or is of doublewalled construction. The conductor which carries a base 7 and guide posts 8 is sunk into the sea bed on a drill string 50 (Fig. 3) connected to the conductor by a coupling 51. The string 50 carries a hydraulic turbine 57 driving a bit 59 and a casing shoe 62 having cutters 63. After sinking is finished the drill string, connector, turbine and bit are removed and the conductor is cemented by means of a cementing tube (65, Fig. 4 not shown) having a coupling (66) and a packer 67. The tube and packer are removed, and the wellhead, pedestal conductor, and buoyancy member are assembled below the drilling vessel and are lowered on a tubing string (71, Fig. 5 not shown) to engage a coupling 18 on the pedestal conductor with the top of the conductor, the descent being controlled by altering the buoyancy of the member 19. A marine conductor (13, Fig. 6 not shown) is connected to the wellhead, the well is deepened and a casing 9 supported from the conductor. After the casing 9 has been cemented, tubing (75, Fig. 7 not shown) is connected to the top of the casing 9, the well is deepened, high density fluid is circulated into the well, the tubing 75 is withdrawn, and casing 10 is supported from the casing 9 and cemented. Before or after the casing 10 is cemented, tubing (77, Fig. 8 not shown) is suspended from the wellhead and coupled to the casing 10, the well is deepened to the oil producing strata 32, high density mud is introduced into the well, the production string 30 is supported from the casing 10 and cemented, and the tubing 77 is replaced by the production tubing 33. Finally the string 30 is perforated, the marine conductor is removed and flow lines are connected to the wellhead. During the substitution of the tubing 75, 77 for the tubing 77, 33 respectively the buoyancy of the member 19 is controlled to keep the load on the pedestal conductor as small as possible. An articulated coupling or a blowout preventer 80 (Fig. 9) may be incorporated in the coupling between the pedestal conductor and the conductor, the casings 86, 91 being supported by the blowout preventer or the conductor. The well is completed by suspending a production tubing from the wellhead and a production string from the blowout preventer. The well may alternatively be completed by replacing the blowout preventer and the apparatus there above by a wellhead seating on the conductor and supporting a production string. The construction shown in Fig. 2 may be modified in a manner similar to the alternative. The production string 30 (Fig. 2) may be replaced by casing and a production tubing may extend through the tubing 33 and the string 30.