Patent GB-846858-A (GB)
Title: Retrievable well packer and anchor
Inventor: JR EARNEST HUBERT CLARK
IPC: E21B33/1295
Filed: 1959-05-15
Abstract: 846,858. Oil wells. BAKER OIL TOOLS Inc. May 15,1959, No. 16732/59. Class 85. In a well packer having gripping members which are expanded by the pressure of well fluid into engagement with the well casing, bypass means are provided which, when the packer is being lowered in the casing, prevent the pressure from expanding the grippers, said by-pass means being closed when lowering is ended, to enable the pressure to expand the grippers. Figs. 1 and la, joined end to end, show a packer assembly in the well casing B with parts in the relaxed positions for lowering in the well, a tubular string E being connected by a sub 12 to a tubular mandrel 10 attached to a lower section of tubing 16. A body 17 is slidable on the mandrel 10 and is anchored against upward movement in the casing B by grippers 20 on pistons 19 slidable in bores 18, the pistons and grippers being maintained in correct orientation by bars 23 bridging the bores 18. The pistons are subjected to pressure on both sides during the descent of the packer, the grippers 20 being kept clear of the wall B by springs 26. The fluid pressure reaches the inner faces of the pistons through by-passes 28, one longitudinal by-pass groove being formed in the mandrel 10 for each longitudinal line of pistons 19. The by-passes connect the spaces above and below the packer as long as the mandrel is maintained, by the engagement of ratchet-like teeth or serrations 96 which encircle the mandrel, with a spring-pressed pawl 87, in a raised position relative to the body 17. The teeth 96 permit only a one-way ratchet movement to raise the mandrel in the body 17. When, as described below, the mandrel falls in the body 17, the packing 30 seals the entrance 31 of the by-passes, the packing 51 seals against the casing B and the backs only of the pistons 19 are subjected to pressure, the grippers 20 being thrust outwardly. When the packing 30 seals the by-passes, the fluid pressure tends to move the mandrel 10 upwardly, which would release the packer from the casing. This is prevented by a floating piston 40 having a skirt 43 which bears on a step 45 on the mandrel 10. The fluid pressure in the by-passes bears on the top of the piston and a downward force is applied to the mandrel to balance the upward force thereon. The packing 51 surrounds a backing sleeve 50 screwed into the body 17 and sliding in a conical ended sleeve 55, a flange 57 preventing withdrawal. Squeezing of the packing between the members 17, 55 expands it against the casing B. The operation of the upward gripping means described above is preceded by and depends upon the operation of downward gripping means comprising grippers 61, housed in grooves 63 in a ring 64 and having drag portions 65 which are pressed against the casing by springs 66, the gripping teeth 67 being thus kept back to prevent wear. The ring 64 is connected with some freedom of vertical movement, to the sleeve 55 by bolts 75 screwed into the sleeve and having heads 77 slidable in bores 76 in the ring. A ring 71 and a sleeve 83 are screwed to the ring 64, and teeth 93 at the upper end of a key 83, vertically slidable in a key-way in the mandrel 10, engage threads 94 in the sleeve. The lower end of the key is, in the initial position; clear of the pawl 87, but rotation of the mandrel relative to the rest of the packer which is held by the drags 65 screws the key down the threads 94 until it sweeps, during the rotation, across a cam face of the pawl and releases it from the teeth 96. The mandrel is now free to fall, the fall first sealing the by-passes 28 and locking the body 17 against upward movement, and then forcing the body 17 downwards by contact of the shoulders 46, 47. This brings the cone face 59 against the grippers 61 which are forced out to hold the lower part of the apparatus against downward movement. Further descent of the body 17 squeezes and seals the packing 51 against the casing. The string E is now turned back slightly, to the extent permitted by a one-way spring stop, to remove the key from the pawl 87 to lock the mandrel again. The packer is now ready for use, and may be retrieved or repositioned by re-engaging the key with the pawl to release the mandrel which is pulled up to re-open the by-passes 28 and relieve the grippers 20, 61 and packing 51. Springy cam-ended arms may project upwardly from the part 32 to engage under a shoulder 114 or in a groove 115 in the sub 12 to releasably hold the mandrel 10 in the "by-passes open" or "by-passes closed" positions.