| 摘要 |
The present invention generally relates to controlling the flow of fluids in a wellbore. In one aspect, a valve for selectively closing a flow path through a wellbore in a first direction is provided. The valve includes a body and a piston surfac e formable across the flow path in the first direction. The piston surface is formed at an end of a shiftable member annularly disposed in the body. The valve further includes a flapper member, the flapper member closable to seal the flow path when the shiftable member moves from a first position to a second position due to fluid flow acting on the piston surface. In another aspect, a valve for selectively closing a flow path through a wellbore in a single direction is provided. In yet another aspect, a method for selectively closing a flow path through a wellbore in a first direction is provided.
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