Complex drilling programs in crowded downhole environments are increasingly common today, placing a premium on effective techniques for avoiding wellbore collisions. The costs of such incidents, both in financial and safety terms, can be extremely high. The authors have developed a comprehensive and effective approach to wellbore collision avoidance, as confirmed by a number of consistently successful projects. Based on their experiences in the field, the authors believe the time has come to establish an industry-wide standard for evaluating, minimizing and mitigating well collision hazards. This paper will outline their approach and provide case studies illustrating the high cost of such collisions and the value of an effective process for identifying-and eliminating or reducing-their likelihood.

The approach described is flexible enough to accommodate the different challenges each unique field presents, and has proven equally effective in projects ranging from simple vertical wells to crowded land pads, offshore platforms, deepwater/subsea and fishbone multilateral designs. Well position uncertainties are determined by using survey error models from the Industry Steering Committee on Wellbore Survey Accuracy. Drilling program recommendations are based on the status and conditions of adjacent wells and the nature and magnitude of potential risks associated with a collision. Developing a standard based on this approach will equip the industry to achieve increasingly complex and ambitious goals without compromising safety or incurring unacceptable losses or risks by ensuring the targeting of the correct limited resources and expertise where they are most needed.

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