US Patent 8424611 Downhole safety valve having flapper and protected opening procedure

A downhole valve has a closure device (e.g., one or more flappers) for closing off the valve. A no-go actuation mechanism protects the flappers from damage. When the flappers are closed, the mechanism prevents a tool from passing into the valve and causing damage to the flappers. Yet, the mechanism may open the valve's flappers when the tool string is forced into the valve. When the valve has successfully opened, then the mechanism moves out of the way of the toolstring so it can pass through the valve. For the mechanically operated valves, operators use a shifting profile in the valve only in the upward direction to return the valve to the closed position. For hydraulic actuated valves, hydraulic pressure may be used or exhausted, depending on the design, to allow the flappers to go closed. Once the flappers have closed, the no-go mechanism is once again realized.