| 摘要 |
A control valve 100 is used in conjunction with a gas lift valve downhole for selectively closing a flow path through a wellbore in a first direction to prevent backflow of gas or fluid from production tubing to an annulus. The control valve comprises a flapper check valve 150 which is allowed to close when a flow tube 155 is shifted against the bias of a spring 130 by a force acting against a piston surface 125 attached to the flow tube 155. The force is created by back pressure acting on closed hinged flaps 120 of the piston surface 125 when the force of a gas pressure which acts to open them is less than a biasing force to close them. |
