| 摘要 |
A first unitary slip located beneath the packing element is set from the surface by the operator by applying the weight of the tubing. Whenever the pressure beneath the packer exceeds the pressure above the packer which would normally cause the packer assembly to be moved upwardly within the casing, the excess pressure is used to drive a setting piston downwardly against a spring, the downward movement causing a setting sleeve to cause an upper unitary slip to rotate into contact with the casing and act as an anchor against upward movement of the tool. When it is desired to retrieve the overall assembly, pulling up on the tubing string causes the pressure to be equalized across the packer assembly and the tool can be removed from the borehole. The spring against which the setting piston works enables the apparatus to be run through fluid while moving through the borehole without a premature setting of the anchor assembly.
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