Abstract: Disclosed is a tester valve having a ball valve rotatable between the open and closed positions for use with a test string to test an oil well. The apparatus includes a ball closing piston in the valve operating mechanism which assists in rotating the ball to the closed position. One side of the ball closing piston is exposed to a first pressure of formation fluid flowing through the interior of the test string on the upstream side of the ball valve. The other side of the piston is exposed to a second pressure which is lower than the first pressure by a pressure drop caused as the fluid flows through the apparatus past the ball being rotated to the closed position. A bypass mechanism is additionally disclosed which is operable for equalizing the pressure on both sides of the ball closing piston when the ball is being rotated to the open position.

Abstract: A valve for use in conjunction with a testing string in an oil well is disclosed in which the valve is maintained in the open position until the valve is placed in sufficient compression to collapse any slip joint which also appears in the testing string. A pressure piston is present in the valve having one surface exposed to the well annulus and a second surface exposed to a pressure in a flow passage through the testing string. The valve includes a rotatable ball valve and a bypass around the ball for equalizing the pressure above the ball with the pressure below the ball for use in opening the valve from the closed position. A spring means in the valve biases the closed ball toward the open position for opening the ball when a pressure difference across the ball is reduced sufficiently to allow the ball to rotate to the open position.

Abstract: Disclosed is an apparatus and its method of operation for an oil well valve having a self adjusting liquid spring responsive to changes in pressure in the well annulus. The valve has a liquid spring contained in a spring chamber divided by a piston means which moves responsive to annulus pressure changes to operate the valve. The piston means includes a metering means to meter liquid from one side of the piston to the other as the volume of the liquid changes due to pressure and temperature changes. The piston means moves responsive to pressure changes in the well annulus which pressure changes are applied to the well annulus at a rate faster than the metering means may relieve the changes. A mechanical spring means in conjunction with the metering means returns the piston means to its original position after a predetermined time.