| 摘要 |
A fishing spear for retrieving a fish from a wellbore comprises a mandrel fixedly secured to an upper sub, a collet assembly telescopically surrounding the mandrel and a support sleeve telescopically surrounding the mandrel and positioned between the mandrel and the collet assembly. An expandable fluid cavity is formed between a portion of the facing surfaces of the support sleeve and the mandrel. A coil spring, which is disposed between the support sleeve and the upper sub, downwardly biases the support sleeve so that it rests against a projecting head at the bottom of the mandrel when fluid pressure is not applied to the expandable cavity. The collet assembly includes a plurality of collet fingers, each having a collet head at the end thereof. The collet fingers are naturally inwardly radially biased in the direction of the mandrel. When the support sleeve rests on the projecting head, the collet heads are radially outwardly displaced or wedged. Before inserting the projecting head into the fish, or when removing the projecting head from fish, the support sleeve is raised by introducing fluid pressure into the expandable cavity, which causes the collet heads to assume their retracted position. When inserting the spear into the fish in this manner, collet fingers, which have low buckling resistance, do not collide with nor are axially displaced by fish.
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