Importance

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Abstract

For use as part of a test string employed to evaluate the production potential of a chosen formation through which an oil well has been drilled, an annulus-pressure-operated sub-surface control valve, typically a ball valve, wherein to deal with the problem of the high pressure of fluid acting on the upstream side of the ball resulting in the frictional forces caused by the ball being pressed up against the seating on its downstream side making the ball stick, the utilization of a differential thread force multiplier by which the actuating force may be applied to the ball. Moreover, to deal with the problem, experienced when employing a biased-closed valve, that the annulus pressure needed to keep the valve open may have to be maintained for extended periods, the invention provides latch means whereby the valve actuating sleeve may be retained in the valve-open position even when the applied annulus pressure is removed, a first pulse of applied annulus pressure causing the valve to open and then, as the pressure is removed, become latched in the open state, and thereafter a second pulse of applied annulus pressure unlatching the valve and allowing it to close once the pulse has ended.

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First Claim