| 摘要 |
A tool for subterranean use employs relative movement between a housing and a piston by pressurizing and removing pressure in a variable volume defined between them. The variable volume is sealed with packer cups preferably with one supported from the piston and the other off the housing and in opposed orientations so that the broad surface area on each packer cup abuts the surface where relative movement takes place. The downhole tasks accomplished with the relative movement can be varied and include tubular expansion, setting packers or shifting sleeves, for example. A single or multiple packer cups are tied to a structure that needs to be driven and building pressure behind a packer cup or reducing pressure ahead of it advance the piston.
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