Harsh barium sulphate scaling downhole presents a significant squeeze treatment challenge, particularly with providing and then maintaining scale inhibitor residual concentration for extended period at and above the high MIC demand. The control situation worsens considerably when faced with such a scenario in a high temperature, naturally fractured carbonate well. Conventional dispersive type squeezes have found favour here, however their placement and subsequent rapid return at high concentration can result in low squeeze lifetime, mainly due to poor retention of the inhibitor type. The paper details a solution to the inhibitor retention and high MIC demand challenges via development of a novel precipitation squeeze formulation which utilises the dispersive type scale inhibitor as its primary active.

The phase-separating ‘precipitation squeeze’ inhibitor formulation is designed to be deployed via conventional bullheaded squeeze into a high temperature, naturally fractured carbonate well environment. The material will thermally activate causing phase separation and enhanced retention of the inhibitor as its calcium salt. Since the active inhibitor is highly tolerant to calcium, it will return into solution with greater facility than conventional precipitation squeeze analogues, leading to elevated levels of scale inhibitor in solution for extended periods compared to standard chemistries in the same carbonate environment.

Simulated carbonate field coreflood tests indicated a 3-4 time squeeze lifetime extension was achievable using this technology, and formation damage assessments indicate no identifiable damage to the core material or fluid throughput. The material is now developed for bulk manufacture and is now in the field awaiting first pilot squeeze deployment at the time of writing this abstract.

This novel alternative squeeze treatment shows significant increase in achievable squeeze lifetime compared to existing scale inhibitor chemistries for squeeze deployment in harsh barium sulphate scaling carbonate field deployments. Benefits are logistical, environmental and economic when deploying this technology.

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