Patent GB-881647-A (GB)
Title: Apparatus for retrieving a drill collar stuck in a well bore
IPC: E21B31/20
Filed: 1959-06-29
Abstract: 881,647. Boring earth &c. LEBUS, F. L. June 29, 1959, No. 22230/59. Class 85. Apparatus for retrieving a drill collar 97 (Figs. 11, 13) stuck in a borehole 81 comprises a wash-over pipe 80, a tool 1 insertable in the pipe during the retrieving, a mandrel 5 forming part of the tool and connectable to the collar, a sleeve 12, 26 movable longitudinally on the mandrel having dogs 21 and piston rings 14 engageable with the pipe, a cage 29 connectable with the sleeve and movable longitudinally on the mandrel, slips 51 carried by the cage adapted to engage the pipe, a bush 10 on the mandrel adapted to open the slips so that when a collar connected to the mandrel is freed from the borehole and together with the mandrel starts to fall down the pipe the slips will engagethe pipe to prevent the collar falling to the bottom of the borehole. Figs. 1, 1A, joined end to end, show the tool and an unlatching mechanism 91. The bush is screwed on to the mandrel, and is slidable longitudinally relative the cage but rotationally fixed thereto. The apparatus is prepared for running into the borehole by placing the tool 1 in the pipe 80 with the tool threads 71 protruding for the attachment of the unlatching mechanism. The nandrel is held against rotation, the pipe is otated, the dogs 21 entraining the sleeves 12, 26 and cage 29 causing the bush 10 to screw downwardly on the mandrel to open the slips. When the slips begin to move, the tool is noved to the desired location in the pipe when i vertical upward movement imparted to the pipe causes the dogs to move the sleeve upvardly until spring loaded fingers 31 on the sleeve lock in notches 56 in the cage. Further upward movement of the pipe causes the cage o force the slips against the bush and grip the pipe. To increase the gripping action, the mandrel is turned in the bush 10. The assembly s then run into the borehole by piping fixed to the pipe. As a pin 96 on the unlatching mechanism approaches the collar, pumped fluid pressure on the rings 14 forces the sleeve into the cage without affecting the slips. Rotation of the pipe screws the pin into the collar. The unlatching means have, so far, been inoperative, the rotational drive between the mandrel and the pin being effected by lugs 112 on the mechanism upper housing 92 engaging recesses 104 on the core 95 extending upwardly from the mechanism lower housing 93 integral with the pin. An upward pull on the pipe shears pins 118, and the unlatching means are operative. Continued rotation of the pipe causes the bush to screw up on the mandrel and release the slips 51 to permit the wash-over pipe and reamer 84 to work down over the collar. The slips may be opened again by raising the pipe, the dogs entraining the sleeves 12, 26 and 29 to lift the slips along the bush, the lugs 112 being either received in recesses 111, or, by a slight turning of the pipe, passed through the passages 110, 109 to allow the pipe, retrieving tool and housing part 92 to be removed from the borehole. When they are again run in, the lugs 112 are guided by inclined faces 107 into the channels 109, 110 and into the recesses 104. When a section of the collar is released, this section is unscrewed by lifting the pipe to place the lugs 112 in the recesses 111, and incidentally to tighten the slips. The joints between sections may be loosened by firing a string shot. After unscrewing, the pipe, tool, unlatching means and collar section are lifted out of the well. When the pipe containing the tool reaches the surface, a pipe string is screwed into the sub 2, an upward movement of the string releasing the slips and allowing the tool to be removed from the pipe. When, during the freeing of a stuck section, it is necessary to add an additional length of piping, it is not necessary to lock the slips in the released position, but instead, pump pressure on the piston rings is increased so that the drag of the dogs on the rising pipe is overcome, and the sleeve 12, 26 is not moved upward. In case of pump failure, the pipe is turned in a left-hand direction which brings a tooth 44 (Fig. 5) on a member 37 into locking engagement with one of the longitudinal key ways 11 in the mandrel 5, further rotation of the member 37 being thereby stopped. A pin 43 on the sleeve part 26 continues to move along an eccentric slot 46 in the member to jam teeth 45 against the mandrel which itself is anchored by the collar, the sleeve 12, 26 thus being held against entrainment by the rising pipe.