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The advent of deepwater drilling and the increasing number of deepwater discoveries have led the energy industry to develop new completion design philosophies and technologies for challenges that did not exist in the oilfield less than a decade ago. As a result, the numerous deepwater developments and the experience gained have led to new levels of efficiency and reliability in completion design; risk and economics analysis have joined the technology, safety, and environmental aspects in educated decision processes.
Two challenges in particular have created opportunities for advancement. First, rig-time costs for operating in deepwater are so high that efficiency and reliability had to be emphasized to minimize nonproductive time during completion installation. The result was the development of special tools and techniques that allow operators to reduce the number of trips in the hole and to accelerate online time on the drill floor.
The effort to decrease nonproductive time paralleled a second important objective: increasing the time of field reliability. Because many deepwater wells are subsea, intervention operations and costs are prohibitive; thus, completions must be designed to minimize or eliminate the need for interventions during the life of the well. This objective intensified the need for better equipment designs with respect to longevity, corrosion, and erosion-resistant materials, work rating specifications, and remote monitoring and control equipment.
Although some deepwater projects are completed with dry trees from platforms, this article focuses on subsea wells and the major drivers that have differentiated their completion design processes from those of conventional designs. It also compares some of the solutions adopted to address risks and economic issues and discusses how these solutions vary according to corporate design philosophies and local best practices. Examples of design solutions are discussed for various deepwater areas, including the Gulf of Mexico, West Africa, and Southeast Asia.