| 摘要 |
A tubing string extends downhole in a cased borehole to a jet perforating gun. A packer device is located uphole of a releasable coupling apparatus. The coupling apparatus has an annular piston therein which is moved to release the lower string. Two spaced apart movable annular pistons are series connected in the tubing string at a location below the packer and above the gun. Flow ports, formed in the tubing wall, are covered by the pistons. A ball of appropriate diameter can be circulated downhole and seated upon either of the pistons, thereby forcing a selected piston in a downhole direction. Circulation ports are provided below the lower piston in proximity of a gun firing head. The lower piston includes a shaft depending axially therefrom and into proximity of a detonator of the gun firing head, so that when the lower piston is forced downhole, the shaft contacts the firing head which detonates the shaped charges of the perforating gun. This assembly of elements enables many different options to be exercised prior to firing the gun.
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