Abstract: Well test apparatus having, in a well, an annulus therearound. An annular housing has a valve for the control of fluid flow through the housing. A pressure chamber is provided within the housing. Lockable pressure trapping means is responsive to annulus pressure for locking in a condition wherein pressure is trapped in the pressure chamber. A piston is responsive to trapped pressure in the pressure chamber and to annulus pressure for control of the valve.

Abstract: Well test apparatus having, in a well, an annulus therearound. An elongated housing has a fluid passage extending longitudinally therethrough and a fluid passage opening and closing means for such passage. A further fluid passage permits fluid flow through the housing from the longitudinally extending passage to the annulus. A differential pressure responsive valve means for the further passage is responsive to pressure in the longitudinally extending passage for urging the valve means open to fluid flow in the further passage from the longitudinally extending passage to the annulus, and is responsive to annulus pressure for urging the valve means to a closed condition for fluid flow through the further passage.