| 摘要 |
This invention relates to a downhole activated device for providing cathodic protection for pipes in a wellbore for the production of hydrocarbons. The downhole activated devices are carried within either the pipe casing or the collars or both and remain generally within the maximum outward profile of the pipe string so as not to interfere with the movement and placement of the pipe string in the wellbore. The pipe string may be rotated, reciprocated and circulated which enhances the ability of the installer to place the pipe string in a deviated or long reach wellbore. Once the pipe string is in place, the devices may be deployed by one of several methods such that pistons mounted in openings in the peripheral wall of the pipe string move outwardly to contact the wall of the wellbore. Such contact with the walls of the wellbore insures that the sacrificial material in the pistons will corrode in preference to the remainder of the pipe.
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