Patent EA-003000-B1 (EA)
Title: Downhole safety valve
Inventor: HEIJNEN WILHELMUS HUBERTUS PAI
IPC: E21B34/08
Filed: 2000-09-21
Abstract: 1. A safety valve for use in a wellbore formed in an earth formation, comprising: - a valve body 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 movable relative to the valve body between an open position in which the fluid passage is open and a closed position in which the closure member closes the fluid passage; - an activating device for selectively subjecting the closure member 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; and - control means for controlling the activating device to subject the closure member to said drag force. 2. The safety valve of claim 1, wherein the activating device is operable between a first mode in which flow of the stream of fluid against the closure member is substantially prevented, and a second mode in which flow of the stream of fluid against the closure member is allowed. 3. The safety valve of claim 2, wherein the closure member is arranged in a conduit and wherein in said first mode the activating device substantially prevents flow of the stream of fluid into the conduit, and in said second mode the activating device allows flow of the stream of fluid into the conduit. 4. The safety device of claim 3, wherein the activating device includes a flapper valve having a flapper element arranged upstream the closure member, which flapper element is rotatable between a closed position in which the flapper element substantially closes the conduit and an open position in which the flapper element substantially leaves the conduit open. 5. The safety valve of claim 4, wherein the flapper element is rotatable about an axis dividing the flapper element in portions of different surface areas, and wherein the control means includes a system for exerting a selected torque to the flapper element, said torque counter-acting initial rotation of the flapper element from the closed position to the open position thereof as a result of flow of the stream of fluid against the flapper element. 6. The safety valve of claim 5, wherein the flapper element is fixed to a shaft rotatable about said axis of rotation and the system for exerting said torque includes a cam surface provided to said shaft and a selected one of a spring activated element biased against the cam surface and a solenoid activated element biased against the cam surface. 7. The safety valve of claim 6, wherein the cam surface includes a substantially flat surface portion of the shaft. 8. The safety valve of any one of claims 5-7, wherein the control means includes trigger means for triggering said initial rotation of the flapper element against the action of the system for providing said torque. 9. The safety valve of claim 8, wherein the trigger means is arranged to trigger said initial rotation of the flapper element when the flow rate of the stream exceeds a selected threshold flow rate. 10. The safety valve of claim 9, wherein the trigger means includes a vane element arranged in the stream and being rotatable about said axis at a fixed angular orientation relative to the flapper element such that the vane element is out of alignment with the stream when the flapper element is in the closed position thereof. 11. The safety valve of claim 9, wherein the trigger means includes a fluidic trigger device having a fluid inlet, a first fluid outlet arranged to direct a substream of the stream of fluid entering the fluid inlet onto a selected one of said portions of the flapper element, a second outlet arranged to direct the substream away from the flapper element, and means for diverting the sub-stream from a selected one of said outlets to the other one of said outlets.