With the trend of economic, regulatory and technological changes, demand of a comprehensive standard to systematically evaluate and manage the risks of wellbore collisions has become significant in offshore oil development. Several accidents happened during normal operations at the Bohai Sea oilfield, including boreholes collision and drilling through adjacent casings. Under this situation, the China National Offshore Oil Corporation (CNOOC) adopted new offshore well anti-collision standard and related remedial measures.

As part of the anti-collision safety operation system in CNOOC offshore oil drilling, the standard is designed and established for requirements mainly in four perspectives, including: data and material collection specifications in the early stage of drilling; anti-collision risk analysis in drilling design; anti-collision safety technical measures in drilling operation and operation site; remedial strategies and operations in case of wellbore collision. In this paper, we also describe how the standard has been applied to the several recent cases, and discuss its benefits for the anti-collision risk control of drilling offshore cluster wells and adjustment wells, treatment cost reduction, and marine environment safety.

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