GB1392967A - Subsea drilling assembly - Google Patents

Abstract

1392967 Screwing drill rods ATLAS COPCO AB 12 July 1972 [12 July 1971] 32549/72 Heading B3N [Also in Division E1[ A drill assembly 11 (Fig. 2) adapted to rest on a sea-bed has rotary-drive mechanism 34 driven by a motor 38, a drill string (not shown) rotated by the mechanism and including a core barrel, a jack 35 axially feeding the mechanism and string, a body 18 (Fig. 12) movable between a surface structure (not shown) and the assembly along a flexible guide 16, 17 (Fig. 9) an inner core barrel 98 (Fig. 12) adapted to be carried by the body and for supply to, or removal from the core barrel, and a retrieving device 82 arranged to be lowered from the body for removal of the inner core barrel from the string. The assembly includes a drill rod magazine 31, a tank 24 having two compartments, a propeller 22 preventing turning of the assembly as it is lowered by the guide from the structure, and hydraulic support legs 13. Feet 30 on the legs have holes for ejection of water to free the legs when sunk in sea-bed. One tank compartment is open to the sea and houses a pump 89 for drilling fluid and a level indicator, whilst the other has a flexible wall 29, is filled with oil, and houses electric motors and pumps controlled from the structure and supplying oil to the motor and jacks driving components of the assembly. The mechanism is mounted on the ram of the jack 35 and is connected to a drive rod 40 by a key 42 (Fig. 13) and shear pins 43 and is prevented from rotating relative the jack 35 by pivoted arms 36. A jack 44 moves a member 45 to increase torque during breaking the joints between drive rod and drill rod or between drill rods. A double chuck 47 having axial movement permitting screwing and unscrewing of string joints is mounted on the jack 35, and may be locked against rotation by a jack 52 (Fig. 9) and member. A clamp 55 (Figs. 2 and 24) is mounted below the tank and a casing clamp 60 is mounted below the clamp 55. The magazine is moved by a ratchet to rotate about the jack 35 and comprises apertured plates 65, 67 vertically holding two casing tubes 105 (Fig. 24) each having an adapter for connection to the rod 40 and of different length, a core barrel and core bit, and drill rods 108. The elements of the string in the magazine are supported by a plate having an aperture opened by a shutter 68 to permit the elements to be fed to the sea bed. The assembly is lowered from the surface structure by the flexible guide which passes around pulleys 72, 73 (Fig. 9) on the jack 35 and comprises parts 16, 17. The parts 16, 17 are respectively fixed to, and guided through the body base-plate 78 (Fig. 12) so that the body may be hauled up from, and down to, the assembly. The base-plate has a rubber seal 79 seating on the top plate 76 of the mechanism, and the pump 89 is arranged to hold the body on to the plate 76 by suction, and to supply drilling fluid up through the outer annulus in the body to pump the retrieving device down through the rod 40 and the drill string. When the body is not seated on the assembly and the assembly is drilling, valves 94, 98 move to direct drilling fluid straight down the rod 40. In operation the sea bed is first drilled by the casing of most suitable length, and the casing clamp is operated to anchor the assembly until drilling is finished.