| 摘要 |
A well packer of the type which is set by hydraulic pressure injected through the tubing string, having a setting chamber between the pistons therein which actuate the packer, wherein one of the pistons is floating while the packer is being lowered to compensate for thermal expansion or contraction and pressure differentials encountered as the packer is lowered in the well in order to prevent undue pressure from being applied to the pistons which could cause the shearing of shear pins holding the packer in unset position which would prematurely set the packer.
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