The job objective in a UK North Sea field was to permanently abandon a well that had poor cement bonding behind the casing across the intended isolation intervals. The challenge was to provide lateral isolation across two separate intervals in the most efficient way possible. Two "perf-and-wash" operations were executed successfully during the well abandonment. The deeper barrier envelope was validated by tagging and pressure testing the plug. The shallower section had been logged prior to the operation and, on completion of the perf-and-wash job, the plug was drilled out to allow for relogging, which indicated more than 76% of the perforated interval had circumferential coverage. After the bond log results were confirmed, a further cement plug was set across the shallow interval by conventional methods and verified by tagging and pressure testing. This paper outlines the detailed design preparations and presents both case histories where these steps were implemented successfully.

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