DOWNHOLE SAFETY VALVE

摘要

A safety valve for use in a wellbore formed in an earth formation, comprising a valve body (6) having a fluid passage for passage of a stream of hydrocarbon fluid flowing from the earth formation via the wellbore to the earth surface, a closure member (18) movable relative to the valve body between an open position in which the fluid passage (12) is open and a closed position in which the closure member closes the fluid passage, and an activating device (30) for selectively subjecting the closure member (18) to a drag force of selected magnitude, the drag force being exerted by the stream of fluid and inducing the closure member to move from the open position to the closed position thereof. The safety valve further comprises control means (46) for controlling the activating device to subject the closure member to said drag force.