| 摘要 |
A cased borehole has a perforating gun suspended in underlying relationship relative to a packer device. A tubing string has a seal assembly connected to the lower end thereof, and an extension tube downwardly extends from the seal assembly. A seal housing is connected to the packer and receives the seal assembly therewithin. The tubing string is run downhole until the end of the extension tube is in proximity of a gun firing head while the seal assembly is unseated from the housing, so that the fluid in proximity of the gun firing head is displaced with clean fluid which flows from the surface, down the tubing string, and out of the end of the extension tube. After the gun firing head is cleaned, the tubing is lowered, the seal assembly is sealingly received within the seal housing, and the gun firing head is actuated by lowering a gun firing device down through the interior of the tubing string, seal assembly, and extension tube, thereby perforating the casing so that production flows from a payzone, through the perforations, into the lower annulus, through a one-way valve of the seal housing, and up the tubing string to the surface of the earth.
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