| 摘要 |
<p>A down hole tool, constructed to be suspended in a well by pipe, includes a housing (42), a circulation piston (82), a biasing member (94) and a pressure-compensation system. The housing defines a flow chamber in open fluid communication with the pipe interior, a bypass port for fluid flow between the flow chamber and the well, a mud chamber in open communication with the well, and a sealed chamber separated from the flow chamber by a sealed interface. The circulation piston separates the flow and mud chambers and is arranged for movement between a first, bypass port-blocking position and a second, bypass port-exposing position in response to pressure in the flow chamber. The biasing member biases the circulation piston to its first position, and the pressure-compensation system limits the pressure difference between the flow and sealed chambers, thereby limiting the pressure difference across the sealed interface. The tool has particular application to tools, e.g. well logging tools, adapted to be connected downhole to a wireline cable connector that is pumped down the well. Methods of use are also disclosed.</p> |
