| 摘要 |
A downhole tool is provided with a pressure-balancing piston disposed within an interior cylindrical bore to have exposure to fluid pressure within an internal fluid chamber on one side and exposure to hydrostatic pressure on the other side. The piston is movable in response to increasing hydrostatic pressure and causes an increase in fluid pressure within the internal fluid chamber in equalization of the internal fluid pressure to hydrostatic pressure. A mandrel telescopically positioned within the housing forms internal spaces defining an internal fluid chamber exterior to the mandrel and having an interior fluid chamber with fluid ports placing the interior fluid chamber and the fluid chamber exterior to the mandrel in communication. The mandrel has a first pressure area A 1 in communication with the interior fluid chamber and a second pressure area A 2 of substantially equal area to the first pressure area A 1 , whereby invasive gas pressure acting on the first and second pressure areas balance the mandrel.
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