| 摘要 |
<p>A string bypass (10) for bypassing fluid around a packer as a testing string is lowered into or raised out of a well bore, the string bypass including an outer case (56) with an inner mandrel (58) positioned therein such that an annular cavity is defined therebetween in which is a reciprocating piston (114). The case and mandrel both have transverse holes (92,112) therethrough, and the piston includes a transverse passageway (138) which provides intercommunication between the holes when the piston is in an open position (as illustrated). A spring (116) biases the piston toward the open postion. A pump is used to inflate the packer and as the pump pressure gradually increases, it provides a net force downwardly on piston (114) which ovecomes the spring force so that the piston is moved to a sealed, closed position in which communication between the holes is prvented. The piston also includes a substantially longitudinal passageway (146) therethrough which provides continuous fluid communication between the pump above the string bypass and the packer below the string bypass.</p> |
