| 摘要 |
Apparatus for perforating a well comprises a tool string (16,206) comprising a perforating gun (210); a hydraulically actuated firing head (208) responsive to a hydraulic pressure differential, said firing head being cooperatively coupled with said perforating gun to actuate said perforating gun when a particular pressure differential is achieved; and a pump (207) cooperatively arranged in said tool string to establish said pressure differential to actuate said firing head. The firing head may comprise a housing; a mandrel having a first surface for exposure to pressure in said wellbore and a second surface for exposure to pressure in the tubing string, said mandrel being movable from a first position to a second position in response to a predetermined pressure differential between said wellbore and said tubing string; and a piston movable from a first, unactuated, position to a second, actuated, position, said piston being retained in said first position when said mandrel is in said first position, said piston having a first surface exposed to the same pressure source which, when greater, will cause movement of said mandrel; and an initiator actuable by contact with said piston. |
