| 摘要 |
A string bypass for bypassing fluid around a packer as a testing string is lowered into or raised out of a well bore. The string bypass includes an outer case with an inner mandrel positioned therein such that an annular cavity is defined therebetween. A reciprocating piston is positioned in the annular cavity. The case and mandrel both define transverse holes therethrough, and the piston includes a transverse passageway which provides intercommunication between the holes when the piston is in an open position. A spring biases the piston toward the open position. A pump is used to inflate the packer, and, as the pump pressure gradually increases, a differential between the pump pressure and well annulus pressure acts against an annular area on the piston and overcomes the spring force so that the piston is moved to a sealed, closed position in which communication between the holes is prevented. The piston also includes a substantially longitudinal passageway therethrough which provides continuous fluid communication between the pump above the string bypass and the packer below the string bypass.
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