| 摘要 |
<p>The invention relates to valves usable downhole and controlled from the surface hydraulically via control lines or by other techniques. The valve has a minimum flow passage which is preferably oriented along its longitudinal axis and a lateral flow passage which opens upon movement of a valve member via applied control pressure from the surface. Alternatively, the valve comprises a tapered needle movable in a throat. When the valve member shifts, additional flow area is exposed to control the backpressure of a fluid by way of hydraulic pressure control from the surface via the control line. The hydraulic control can be with a single control line acting on a piston attached to the valve member with a return spring opposing such movement, or alternatively, can be carried out with a pair of control lines to actuate reverse movements of the valve member. A pressurized gas chamber can be used to act as the closing force opposing applied pressure from the control line for a return of the valve to its minimum flow or maximum throttle position. Alternatively, an acoustic, electric or other type of surface-directed signal can change the valve position.</p> |
