Patent GB-1343897-A (GB)
IPC: E21B7/12
Filed: 1971-03-10
Abstract: 1343897 Boring earth and rock; wells &c SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 10 March 1971 6446/ 71 Heading E1F A well re-entry tool comprises a tube 20 adapted to be connected at one end to suspension means, e.g. a pipe string, and having a seat 23 for supporting an orienting device 27 so as to protrude from the tube and at its other end a bumper head 30 which extends outwardly from the tube so as to protect the device 27 by maintaining it spaced from a guide funnel 10 as the tool is lowered into a well entrance 9. The tool may be automatically connectable to and releasable from the wellhead. As shown in Fig. 1, the device 27 is an acoustic transmitter/receiver enabling an operator on a surface vessel (not shown) from which the tool is suspended on the pipe string to manoeuvre the tool into the entrance 9 by means of a lateral water jet 22 in response to echoes from reflectors such as 13. After the bumper head has seated on a casing hanger 14 a -shear pin 31 is broken by the weight of the pipe string and the pipe 20 extended some distance into the well, to prevent inadvertant withdrawal, while a marine riser is lowered down the exterior of the pipe 20 which acts as a guide. The riser is latched to a groove 33 on a casing 5 and the tube 20 withdrawn, picking up the bumper head by a seat 32. In an alternative embodiment, Fig. 2, the bumper head 50 forms part of the tube: 51 and has spring loaded latch dogs such as 57 which are biassed outwardly by the orienting device 53 when it rests on the seat 54. The tool is guided to the well entrance as described above and is lowered in the casing 59 until the dogs 57 snap into an annular recess 58. Each dog 57 has a flange behind which the end 87 of a spring loaded rod 71 engages to prevent retraction of the dog when the device 53 is withdrawn. Using the tube 51 as a guide a riser 60, blow out preventer 64 and coupling 61 are lowered into the casing 59. A lower rim of the coupling 61 engages levers such as 70 to release each rod 71 so that the latch dogs 57 are retracted by spring action, so that the tube 51 may be withdrawn. The riser is latched to the casing 59 by actuating hydraulic latches 68 to engage a dog 66 in a recess 67. In a third embodiment, Fig. 5, the bumper head is formed by inner and outer parts 125, 126 of a cementing shoe. The outer part 126 is connected to a casing shoe 121 by a latch 127 and is lowered on a casing string 120 to a suitable depth. The inner part 125 is coupled to a cementing string 140 and lowered through the casing to engage with the outer part 126 by a latch 130. Further lowering of the string 140 releases the latch 127 from the casing shoe 121 and both parts 125, 126 are extended below the casing far enough to expose a lateral guide jet (not shown) in the string 140. The cementing string 140 is lowered together with the casing 120 using the orienting device 145 as previously described until the parts 125, 126 enter the well far enough to prevent inadvertent withdrawal. The orienting device 145 is removed and the casing 120 landed on the wellhead. The cementing string is raised until the latch 127 re-engages the casing shoe 121. After cement has been passed into the well down the string 140, the string is unscrewed from the part 125, and withdrawn whereupon a valve 136 closes to prevent cement backflow. The parts 125, 126 are of drillable material so that further drilling involves lowering the drill through the casing 120 and drilling through the parts 125, 126 and the cement. In a further embodiment (Fig. 4, not shown) the bumper head is a cylindrical shroud surrounding a roller bit, and is disconnectable therefrom on breaking a shear pin, to enable the bit to enter the well. When the orienting device is removed from the centre of the drill it is replaced by a drilling insert piece. In another embodiment (Fig. 6, not shown) the bumper head comprises pivotably spring loaded arms which extend outwardly to protect the orienting device from engagement with the guide funnel. The funnel may be frusto-conical or a truncated pyramid. The top surfaces of the bumper head are angled to reflect noise from the lateral guide jet away from the orienting device.