Patent ID: 8905139

Claim:
A mandrel for isolating production zones in a wellbore, the mandrel defining a through passage smaller than an exterior portion of the mandrel comprising: a) a blapper valve operatively connected to the mandrel; b) a valve actuator, the valve actuator comprising: i. a piston chamber separate from the through passage; ii. a piston with a first side oriented toward the valve and a second side oriented away from the valve, the piston being disposed within the piston chamber; iii. an incompressible fluid between the second side of the piston and a pressure barrier, the pressure barrier being positioned between the incompressible fluid and a compressible gas and; wherein upon breach of said pressure barrier the piston moves within the piston chamber and the blapper valve can be actuated into at least a first position wherein said blapper valve is open and said through passage is open or at least a second position wherein said blapper valve is closed and said through passage is closed.