Patent ID: 9133686
Filing Date: 2015-09-15
Classification: E21B

Abstract:
1. A method of operating a downhole tester valve comprising: positioning the downhole tester valve at a location in a wellbore, the downhole tester valve having an operating fluid chamber, a biasing fluid chamber and a power fluid chamber; applying increased annulus pressure to the power fluid chamber to pressurize operating fluid in the operating fluid chamber; applying the pressurized operating fluid on a piston assembly of the downhole tester valve to shift a valve assembly of the downhole tester valve from a closed position to an open position; responsive to predetermined travel of the piston assembly, opening a bypass passageway for the pressurized operating fluid to charge biasing fluid in the biasing fluid chamber; equalizing pressure in the biasing fluid chamber and the operating fluid chamber by passing operating fluid through a metering section of the downhole tester valve at a first predetermined rate; and reducing annulus pressure at a second predetermined rate based on the first predetermined rate to retain the valve assembly in the open position without the continued application of the increased annulus pressure.