Underbalanced technology is typically understood as a drilling technique, not a completion technique. Yet in many fields where underbalanced (UB) technology is applied, the completion aspect can have considerably greater economic impact - after all, the completion is the crucial link between the reservoir and hydrocarbon flow throughout the life of the well.

The advent of new technology and techniques have allowed UB to be applied to completions in both hard rock environments and in wells requiring support from screens or liners. Successful UB-completed wells have been documented in heavy oil, light oil and gas environments, and in horizontal and vertical wells. In every environment, understanding and controlling pressures and fluids are the keys to success.

This paper discusses the elements of the completion process that are unique to underbalanced operations and then examines five field case histories that highlight the role of UB.

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