| 摘要 |
A firing head for a tubing conveyed perforating gun is shown which is operated by pressuring the interior of the tubing string. A sliding sleeve having a pressure responsive seal area changes position at a predetermined increase in tubing pressure. As the sleeve changes position, the production ports of the tool are first opened, allowing communication between the well annulus and the tubing interior. Movement of the sliding sleeve also drains an initially filled, hydraulic cylinder within the interior of the tool. As the cylinder is drained, an associated fluid piston moves to occupy the evacuated chamber. The fluid piston is connected to a firing pin holder which releases the firing pin, allowing the firing pin to contact a percussion detonator to fire the perforating gun.
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