Patent GB-873479-A (GB)
Title: Improvements in or relating to off-shore drilling and other underwater operations
Inventor: STRATTON HAL
IPC: E21B43/10
Filed: 1957-09-03
Abstract: 873,479. Boreholes. SHELL OIL CO., CONTINENTAL OIL CO., SUPERIOR OIL CO., and UNION OIL CO. OF CALIFORNIA. Sept. 3, 1957, No. 27716/57. Class 85. A well conduit is set in a formation underlying a body of water by drilling a hole from a floating vessel, the diameter of the hole being greater than that of the string used for drilling it; by guiding the conduit down the string into the hole during or after drilling, and by maintaining a laterally flexible connection between the vessel and the conduit whilst the conduit is anchored in the hole. Mounted on the vessel 10 are a mud tank 39, a drawworks 14, a drilling rig 18, and a rotary table 25 mounted on gimbals over a collar 27. A receiver assembly (Fig. 3) comprises a sleeve 56 welded to arms 69 and to the well conduit 32, and guide posts 59 extending upwardly from the arms. A circulating head 31 comprises a well conduit seal 74, a drill pipe seal 90, a nipple 83 adapted to be attached to a mud return hose 42, and sleeves 148, 153 adapted to engage the posts 59. The well conduit seal comprises a resilient ring 76 which is contracted by hydraulic pressure to grip the well conduit. The drill pipe seal comprises a ring (Fig. 4, not shown) adapted to grip resiliently the drill pipe 34 and rotatably mounted within the head. Prior to drilling of the hole 13 the head is sealed to the conduit, and the head and receiver are suspended beneath the vessel by lines 33 running from the guide posts to points 33A on the vessel. The drill pipe carrying a bit 35 and an under-reamer 36 is positioned to extend through the receiver and head to the formation 12. The drill pipe is rotated by the table to start the hole, sea-water or mud from the tank being pumped down the pipe to free cuttings from the hole. After the hole reaches a depth slightly greater than the length of the conduit, the rotation of the drill is stopped, the bit is raised slightly from the bottom of the hole, and the guide lines are lowered to allow the head and the receiver to slide down the drill pipe until the conduit is positioned within the hole, mud being pumped through the return hose to prevent cuttings entering the space between the drill pipe and the conduit. The conduit is allowed to settle in or is cemented to the formation. The drill pipe is withdrawn from the hole by releasing the conduit seal and hoisting the drill pipe, the bit engaging an internal shoulder in the head so that the head is raised to a position within the cellar. The drilling of the hole then procedes in the manner described in Specification 873,477. In the modification shown in Fig. 8 the initial part of the hole is drilled and the conduit is positioned simultaneously. The conduit 170 is rotatable within but bears upon a sleeve 172 of the receiver assembly which has anchor members 175 and guide posts 174. The drill pipe 181 carries a bit and under-reamer 185 and is coupled during the drilling to the conduit by plugs 183 which are moved by mud pressure to engage the conduit. The conduit has serrations 186 which assist in drilling. Specification 873,478 also is referred to.