| 摘要 |
The valve assembly disclosed herein is used primarily in oil or gas well servicing to prevent contamination of fluids used to treat the formation. The valve is coupled into a tubing string, and it includes a slidable hollow mandrel, with a hingable flapper disk positioned below the mandrel. The valve is generally used in cooperation with a packer tool and bridge plug. When treating fluid is pumped down the tubing string it pushes the flapper disk open and holds it open, so the fluid can reach the formation interval being treated. To treat the next higher interval the packer is unset to raise the tubing string. Releasing the packer allows residual fluids to backflow from the well casing annulus into the tubing string. In this tool the backflowing fluid closes the flapper, so that it acts as a check valve to prevent contamination of the treating fluid. Before the valve is pulled out of the casing the mandrel is slid downwardly, to push the flapper open and hold it in open position.
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