RELEASABLE SPEAR FOR RETRIEVING TUBULAR MEMBERS FROM A WELL BORE

摘要

RELEASABLE SPEAR FOR RETRIEVING TUBULAR MEMBERS FROM A WELL BORE A releasable spear for retrieving tubular members from a well bore has a top member connected to a mandrel which in turn is connected to a lower member, the remote end of the member from the mandrel being adapted to secure a cutter. Rotatably and longitudinally slidably disposed about the mandrel is a sleeve having a tapered portion which is arranged to mate with and slidably cooperate with a corresponding taper on the inside diameter of a grapple carrier having grapples. In a nonexpanded position of the grapples the grapple carrier is located on wedges but upon rotation of the sleeve by a dog clutch so the wedges locate within a longitudinal keyway of the grapple carrier and the grapple carrier 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 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 of the members and mandrel 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 is provided on a sleeve to suit a thread on the well head to be cut. In a further embodiment, again instead of using grapples a two part sleeve is provided with a cam and radially expandable pins which are driven outwardly by rotation of the cam to engage with the internal surface of a tubular member to be cut.