| 摘要 |
In accordance with an illustrative embodiment of the present invention, a pressure controlled reversing valve for use in drill stem testing includes a housing having reversing ports that normally are closed by a valve sleeve that is mounted on a spring-loaded actuator mandrel, stop means for preventing opening movement of said actuator mandrel, a mechanical counter for disabling said stop means and enabling such opening movement only after a predetermined minimum number of pressure increases have been applied to the fluids standing in the pipe string in which the reversing valve is connected, and means responsive to a subsequent pressure increase for reclosing the valve sleeve and reactivating the stop means.
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