| 摘要 |
<p>A method to control a main valve in a well includes providing a pilot valve in the well, energizing an actuator to establish an energized state of fluid communication between the main valve and the pilot valve, thereby putting the main valve in a first state; and de-energizing the actuator to establish a de- energized state of fluid communication between the main valve and the pilot valve, thereby putting the main valve in a second state.</p> |
