Long-term downhole restrictions could potentially create unfavorable impacts for operators: impeding or preventing production and any further interventions. A well in offshore East Malaysia had encountered a stuck Wireline Retrievable Safety Valve (WRSV) issue, with its lock-mandrel partially parted after several unsuccessful fishing attempts. The attempts were finally aborted, leaving the stuck WRSV downhole without a fishing neck for almost 25 years.

In July 2019, initial engagement was made to re-establish access to this well for perforation and production. The solution was to use an Electric Line (EL) milling tool with a tractor and customized milling bit. The aim was to unlock the lock mandrel, which was holding the safety valve in place, and minimize any trace impact of milling on downhole accessories as ability to re-utilize the nipple profile for future safety valve deployments was also targeted, hence maintaining the assembly in a functional state was crucial.

This EL milling method has proven to be an efficient means of performing the operation with minimal: cost, manpower requirement, and operational timeline.

This paper describes the process of designing the operation, and the subsequent execution phase.

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