| 摘要 |
<p>A method of operating a valve in a testing string having a flow channel therethrough and located in a fluid filled well bore, comprising the steps of: providing a sealed chamber in the testing string; creating a pressure differential between the pressure in the sealed chamber and fluid pressure in the well bore, wherein the pressure in the sealed chamber is independent of the pressure in the flow passage of the testing string, applying weight in the testing string onto an operating mandrel means in the testing string, thereby moving the operating mandrel means in a first direction, increasing the fluid pressure in the well bore by a predetermined amount, thereby increasing the pressure differential, and applying the increased pressure differential across a piston on the operating mandrel means, thereby overcoming the weight added to the operating mandrel means, and moving the operating mandrel means in a second opposite direction.</p> |
