| 摘要 |
<p>A hydraulic valve operating circuit for providing positive opening and closing of a downhole safety valve includes shut-off valves which prevent leakage of fuel to the outside environment if a leak should occur in the hydraulic lines which are connected to the hydraulic actuator of the downhole safety valve. A hydraulic control line is connected to the actuator of the safety valve through a normally-closed shut-off valve and the hydraulic control line is also connected to the actuator of the shut-off valve to hold both the shut-off valve and the downhole safety valve open when the hydraulic line is pressurized. Another valve moves to a position to direct the flow of fluid from the safety valve to an accumulator when the pressure in the control line falls below a predetermined value to insure that the downhole safety valve will close properly. The accumulator and the actuator control valves can be replaced by a single gate valve having a novel porting arrangement as shown in one embodiment of the present invention. The gate valve can be adapted for use with either a balanced or a nonbalanced downhole safety valve.</p> |
