| 摘要 |
In a well testing tool having a spring whose biasing force is supplemented by the hydrostatic pressure in the well annulus at the testing depth, a method and apparatus for isolating the spring from the pressure in the well annulus utilizing the pressure differential between the well annulus and the testing tool bore which exists after the formation is isolated. An insolation valve is provided whose closing force is generated by isolating the testing tool bore from the well annulus, and then increasing the well annulus pressure above the hydrostatic pressure. The pressure differential thus created is utilized to close the valve. The opening force is generated by compressing a spring as the valve is closed. Thus, an isolation valve is provided which is normally open and which closes only after the well annulus pressure exceeds a reference pressure trapped in the bore of the testing tool by a predetermined amount. |
