GB1008398A - Drilling underwater wells - Google Patents

Abstract

1,008,398. Sub-aqueous boring. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. June 20, 1962 [June 22, 1961], No. 23773/62. Heading E1F. An offshore well is drilled and equipped from an operational platform 11 by forming a foundation assembly 30, inserting a string of surface casing 25 through the assembly, releasably connecting together the casing and the assembly, suspending the casing from the platform, inserting a drill string 24 having a bit 36, 37 through the casing, drilling a hole 56 in the floor 13 with the bit, lowering the casing so that the lower part of the assembly is received in the hole, and cementing the assembly in the hole. The casing and assembly are releasably attached to a drillable member 46 (Fig. 2B) during initial spudding operations by the bit. After spudding the assembly is lowered into the hole and drilling commences, sea-water being pumped down the drill string and returned through the mud line 53. After the hole for the assembly has been drilled the assembly is lowered into the hole by adding casing. Cement is pumped down the drill pipe or casing to fix the assembly. The casing is released from the member 46 and raised slightly prior to extending the hole for the casing after opening out the hole in the member 46, a tight joint between the top of the assembly and the casing being formed by the seal 43 (Fig. 2A). During drilling, mud is pumped down the drill string and discharged from the annulus between the string and casing into a settling tank. When the hole is deep enough for the casing sufficient casing is run into the hole to reach the top of the assembly, the top of the casing having a casing head 101, 105 (Fig. 9) carrying a drilling wellhead 65 blowout preventers 67, 68 and a riser 72 (Fig. 4) connected to drill pipe 24 for lowering. Cement is pumped down the drill pipe to fix the casing, fluid in the well being discharged through the mud line 53. A marine conductor 75 having blowout preventer 76, buoyancy tank 81, and telescopic joint 80 is stripped down over the drill pipe, the preventer 76 engaging the riser 72. A bit is run through the apparatus and a hole drilled for production casing 97. The bit is withdrawn, a remotely controlled manipulator 84 for turning locking screws is landed on the wellhead 65 and the casing 97 is run in and cemented into the well, the casing having a hanger 100 (Fig. 9) which is locked in position by screws 102. A tubing string 115 is run into the well on a pipe 118 and supported by a hanger 112 having flow passages 116. The wellhead 65 and equipment above it are stripped up over the pipe 118, and a production head 122 is stripped down over the pipe 118 and locked in position on the casing head. The pipe 118 is removed, the wellhead is closed in, and the manipulator removed to complete the well. Specifications 948,322 and 1,008,399 are referred to.