Patent GB-888752-A (GB)
Title: Improvements in well tools
Inventor: BROWN ORA ALEX
IPC: E21B31/20
Filed: 1959-07-21
Abstract: 888,752. Drilling oil-wells. JOY MANUFACTURING CO. July 21, 1959, No. 24964/59. Class 85. A well tool, shown in Figs. 3, 3a, 3b joined end to end, for retrieving drilling equipment lodged in a well bore by means of a washover pipe string 17 having a section 20 which controls the action of the tool, comprises a mandrel 21 capable of longitudinal movement within the pipe string and carrying means for grasping and holding the fish, means 30, 31 for connecting the pipe string 17 initially to the mandrel for rotating the latter for connection to the fish, the means being releasable for longitudinal movement of the mandrel relative to the pipe string, and a catcher assembly 24 for bringing the fish and attached mandrel parts gently to rest when they fall in consequence of the wash-over pipe having removed the obstruction, the assembly being releasably carried by the mandrel and provided with stop means 95 for landing on a shoulder 28 on the section 20, the mandrel being brought to rest when a shoulder 106 engages the top of the assembly 24. When the well tool is run into a well hole, shear pins 30, 31 connect the control section 20 of the wash-over pipe string 17 to parts 36, 37 of the mandrel which have dog-clutch teeth 38, 39 securing the parts against relative rotation whilst the teeth remain engaged. The pins 30, 31 project into L or J shaped slots 32, 33 and the pin 30 has an auxiliary reduced section shear portion 34 which projects into a hole 35. The string 17 and mandrel are thus initially operable as a unit for raising, lowering or rotating as required to connect the tool to the fish. When the tool has been rotated sufficiently to become firmly lodged in the fish, further strain on the shear portion 34 will shear it and leave the pins 30, 31 free to move in the lateral parts of the L or J slots 32, 33 so that the string 17 may be turned relatively to the mandrel to such an extent that the pins 30, 31 lie at the bottom of the vertical parts of the L or J slots 32, 33. In this position, upward movement of the string 17 moves the pin 30 up the slot 32, the part 36 being prevented from rising by its connection to the fish, but the part 37 rises with the string 17 because of the friction of a swab 126 and members 109. The clutch teeth 38, 39 are thus disengaged. If desired the shear pin 30 may now be broken by torque from the string 17, the pin 31 being unstressed because of the disengaged teeth 38, 39. The string 17 is now free to move further longitudinally until splines 67 on the part 53 of the mandrel engage splines 66 on the part 37 whereby torque may be applied to the fish grasping means, and the shear pin 31 broken. If it is undesirable to shear the pins 30, 31 by torque, they may be sheared by longitudinal movement of the string 17. When the pin 31 is sheared, the wash-over pipe may move downwardly without limitation. If it is desired to leave the fish in the hole whilst some other operation is effected, the string 17 is lowered to disengage the splines 66, 67 and re-engage the clutch teeth 38, 39. The part 36 is then turned backward by the string 17 and a shear pin 49 is broken allowing the part 36, which has square non-locking screw threads 42, to unscrew from the socket 43 connected to the fish. Ratchet like teeth 45, 46 ride over one another. The tool may now be taken out of the well, leaving the socket 43 available for re-connection. When the fish has been dislodged, it will fall with the attached parts of the mandrel. This fall is checked firstly by the swab 126 which is moved upwards by well pressure to seat against the nut 131 and close well fluid passages 130. Also, the fall of the fish, and the part 53 of the mandrel removes a stop 78 from a spring-closed flap valve 74 whereby the flow of well fluid up through the centre of the mandrel is checked. The catcher assembly 24 comprises a number of segments 90 pressed outward by coil springs 93a and mounted on a body member 82 which is prevented from sliding on an upwardly enlarging tapered part 101 of the mandrel by a shear pin 98. When during the hydraulically retarded fall of the fish &c., the faces 95 of the segments 90 reach the shoulder 28, the pin 98 is sheared and the fish and mandrel continue to fall through the assembly 24, the increasing diameter of the part 101 gradually closing the fluid passageway between the assembly and the part 101. At the same time, the torque members 109 pass into the section 20, and by rotation of the string 17, spring into key ways 29 in the section 20, so that rotational drive between the string and the fish is maintained. In this condition, the fish is removable from the well by lifting the string 17.