Patent GB-916579-A (GB)
Title: Milling apparatus for removing objects from well bores
Inventor: KEITHAHN JULIAN DMITRI
IPC: B23C3/00
Filed: 1960-02-11
Abstract: 916,579. Oil wells. BAKER OIL TOOLS Inc. Feb. 11, 1960, No. 4887/60. Class 85. [Also in Group XXII] A milling-apparatus for removing objects, e.g. packers, from a well casing, comprises a washover shoe 53, having known cutting means such as tungsten carbide or diamonds held in a matrix, on a tubular shank 51 driven through clutch means 57 from a rotary string D, the shoe 53 being centred by a mandrel 24 which is engaged in the centre passage 11 of the packer B. The packer shown comprises a resilient sealing body 23, upper and lower slips 18, 20, a slip-setting sleeve 17 and slip expanders 19, 22, all on a tubular mandrel 10. The milling-apparatus is designed to remove portions of the members 17, 18, 19, 23, 22, 20 adjacent to the well casing C leaving the rest of the packer within the shank 51 to be removed from the well therewith. When the milling- apparatus is run into the well, a pilot mandrel 27 enters the bore 11 of the packer and cam ends 31 of spring fingers 30, carried by a spring- pressed, axially slidable ring 33, are contacted by the upper end of the mandrel 10. This moves the ring 33 upwards, releases the ends 31 from the sub 37 rotatably screwed on the mandrel 27, and allows the fingers 30 to be cammed inwardly to pass into and through the bore 11, when they spring outwardly. The shank 51 is welded to a clutch part 55 which is slidable on the mandrel 24 and has clutch dogs 57 which, when the shank 51 is in its uppermost position relatively to the mandrel 24, engage dogs on a sub 25, the tool 53 being thus rotated. The mandrel 24 descends in the bore 11 as the packer parts are milled away, drilling fluid being pumped through the string D, ports 60 and longitudinal grooves 61 to the tool 53. The grooves 61 end in a barrier 62, further grooves 63 beyond the barrier conducting small particles from the cutting, which may otherwise tend to jam the mandrel 24 in the bore 11, to the space below the bore. When the packer has been freed by the milling, the string D is raised and removes the sub 25 from the clutch part 55, and the shank 51 and the packer within remain stationary until the spring fingers 30 contact with a shoulder 16 on the mandrel 10, the fingers being locked against the seat by the cam action of the sub 37. As shown, the shoulder 16 is the valve seat of a spring-closed flapper valve 13. Continued raising of the string should raise the milling-apparatus and the enclosed packer, but if, for some reason, the packer will not rise, the string is rotated in a direction to screw the sub 37, which is held stationary, down on the threads 38, the cam ends 31 thus being released to enable the shoulder 16 to cam them inwards to pass into the bore 11. The mandrel 24 will then rise through the stationary packer mandrel until spring-pressed segments 70 snap into a circular recess 77 in the mandrel 24 to entrain the latter with the shank 51. The milling- apparatus is thus withdrawn from the casing leaving the stuck packer. If, when the segments 70 are in the recess 77, it is desired to restart milling, downward movement of the string D cams the segments out of the recess, and the cam part 55 is free to rise on the mandrel 24 until the clutch dogs are re-engaged.