Wellbore system having non-return valve

Abstract

In a wellbore system, non-return valves placed in one or more well boreholes within the system. The valves are placed in the production string downstream from the producing zones, the valve having a closure member selectively biased to a closed position against flow from the producing zones. A fluid backpressure in the production string further operates to bias the valve to the dosed position. When the fluid backpressure is reduced, the force exerted by the flow from the producing zone against the closure member is sufficient to move the closure member in its open position. The closure member is maintained in its open position as a result of the force exerted by the flow from the production zone. An increase in fluid backpressure on the valve results in the movement of the closure member from the open position to the closed position.

Dependencies are inferred from the claim text.