Patent GB-1516491-A (GB)
Title: Well drilling method and apparatus therefor
IPC: E21B7/20
Filed: 1977-01-10
Abstract: 1516491 Boring earth; wells etc. A-Z INTERNATIONAL TOOL CO 10 Jan 1977 [6 May 1976] 00732/77 Heading E1F A method of drilling a well bore and setting a liner therein includes the steps of detachably mounting a liner 28 having a gripping assembly therearound on a drill string 26 having a drill bit and reamers at its lower end, lowering the drill string and liner into the well bore, rotating the drill bit to deepen the well, manipulating the drill string to set the gripping assembly which supports the liner in the well bore, disconnecting the drill string from the liner and removing it, lowering a cementing string (not shown) into the well bore into sealed engagement with the liner, pumping cement through the cementing string and upwardly around the exterior of the liner, and removing the cementing string from the well bore. As described the drill string 26 carries at its lower end (Fig. 1D) drill collars 22, centraliser 24 and a mud motor 21 which rotates a drill bit 14 (Fig. 4D) and three reamers (only one shown, Fig. 4D) whose cutting diameters progressively increase in an upward direction. Each reamer includes a roller cutter 144 mounted on an arm 140 pivoted on a pin 142 on outer mandrel 138. The arm 140 is urged outwardly by a block 148 on inner mandrel 150 engaging a cam surface 146 on the arm 140, the inner mandrel 150 being connected to the upper part of a sliding joint (not shown) so that setting down on the drill string 26 after the bit 14 has reached the bottom of the bore causes the arm 140 to be moved outwardly. Drilling fluid is supplied to cutter 144 through nozzle 154 containing a wear resistant insert. The liner 28 is detachably mounted on the drill string 26 by a threaded collet 34 (Fig. 1A) which is urged into engagement with a threaded sub 44 at the top of the liner 28 by wedge surface 32 on the drill string 26. The drill string 26 is detached from the liner 28 by rotating the drill string 26 to unscrew collet 34 from sub 44. The liner 28 carries a sealing assembly 70 (Fig. 1B) consisting of cup shaped seals 38, 40 which seal against the well casing. The liner also carries a gripping assembly (Fig. 1C) consisting of a mandrel 76 slidably mounted on the liner 28 and having drag springs 82 and gripping members 78, 80. The liner 28 has a pin 84 located in J-slots 88, 90. When the pin 84 is in slot 88 the gripping members 78, 80 are held clear of wedge surfaces 92, 94 but when in slot 90 the wedge surfaces 92, 94 can be moved behind the gripping members 78, 80 to force them into contact with the well casing and thus support the liner 28 in the casing. In use, after drilling, the drill string 26 and liner 28 are manipulated to set the gripping assembly and the drill string is unscrewed from the liner 28 and removed, leaving the liner 28 supported in the well casing. A cementing string (not shown) is then run into the liner 28 and a cementing plug forces cement out of the bottom of the liner 28 and up the annulus between the liner 28 and the well bore and/or casing. The cementing string cooperates with the liner 28 to provide a channel by-passing the seals 38, 40 so that the annulus is cemented above the seals 38, 40.