GB1199080A - Method and Apparatus for Offshore Deep Drilling from a Floating Platform - Google Patents

Abstract

1,199,080. Boring earth &c. CHEVRON RESEARCH CO. 23 Aug., 1968 [24 Aug., 1967], No. 40528/68. Heading E1F. A sub-aqueous well having submerged wellhead equipment carried by casing is deepened by drilling apparatus suspended on the free end of a pipe extending from a reel mounted on a floating platform, the pipe and apparatus being fed to and removed from the well by a gripper supported on the hook of a travelling block. The well 15 is initially drilled and fitted with the casing and the wellhead equipment in accordance with the invention of Specification 839,499, the equipment including blowout preventers 89, 91, 99, a drilling head 101, and guides 73 extending to the platform 10. The platform has a removable rotary table 424 for the initial drilling. The reel 326 is driven by a motor 340 and has a pipe bender and level winder 327, the pipe 324 extending from the bender to the gripper 328 which is supported by the travelling block 31. Drawworks are operative to compensate for changes in elevation of the platform above the water bed to give a constant load on the drill bit, and include a winch drum 416 driven by a clutch 418 set to maintain a constant tension in the derrick line 422. The pipe is steel or aluminium comprises an inner tube having pins to centre it in an outer tube, the .fins adjacent the free end of the pipe connecting the tubes together. The drilling equipment comprises a bit 380, a "down-the-hole" motor 382 operated by drilling fluid to rotate the bit, collars 384, 386, a bumper sub 388, collars 390 392 and a member 394. The member 394 which may be a pump driven by a motor 412 operated by drilling fluid has openings 396 through which the drilling fluid passes to the annulus between the tubes of the pipe, fluid from the annulus passing through treatment apparatus 364 to a tank 360. Fluid from the tank is pumped by pump 356 to the inner tube of the pipe. The pressure in the hole below the drilling head is maintained slightly greater than the static pressure on the head to prevent dilution of the drilling fluid by water. The drilling equipment is guided to and from the well by a yoke engaging the guides and adapted to rest on the bit or the funnel 117 of the drilling head. Heavy drilling fluid from a tank 312 may be fed down a kill line 95 to the annulus between the drill pipe and the borehole.