| 摘要 |
<p>A releasable spear for retrieving tubular members from a well bore has a top member (1) connencted to a mandrel (2) which in turn is connected to a lower member (3), the remote end of the member (3) from the mandrel (2) being adapted to secure a cutter (not shown). Rotatably and longitudinally slidably disposed about the mandrel (2) is a sleeve (4) having a tapered portion (45) which is arranged to mate with and slidably cooperate with a corresponding taper (51) on the inside diameter of a grapple carrier (5) having grapples (50). In a non-expanded position of the grapples (50) the grapple carrier (5) is located on wedges (7) but upon rotation of the sleeve (4) by a dog clutch (60, 61) so the wedges (7) locate within a longitudinal keyway (8) of the grapple carrier and the grapple carrier (5) slides downwardly over the keys thereby radially expanding the grapples. By increasing the tension on the drilling string so the radially outward pressure of the grapples (50) upon the internal surfaces of the tubular member to be machined is increased. Whilst maintaining the drilling string in tension fluid is pumped through internal passages (10, 22, 36) of the members (1, 3) and mandrel (2) to radially extend the cutter and the spear may then be rotated to sever the tubular member whilst the drilling string is in tension.
<??>In another embodiment, instead of grapples an external screw thread (401) is provided on a sleeve (400) to suit a thread on the well head to be cut. In a further embodiment, again instead of using grapples a two part sleeve (421, 422) is provided with a cam (440) and radially expandable pins (430) which are driven outwardly by rotation of the cam to engage with the internal surface of a tubular member to be cut. </p> |
