| 摘要 |
A downhole valve for insertion in a production tubing string permits recirculation of fluid pumped into the casing annulus. The valve includes a cylindrical housing defining an opening, an internal mandrel disposed within the housing, defining a central bore and defining an opening, a valve between the housing and the mandrel, wherein said valve opens to allow fluid communication from the mandrel central bore to the annulus space in response to a pressure differential between the mandrel central bore and the annular space, and biasing means for biasing the valve in a closed position. The valve may be set within a completion string by wireline techniques
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