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An exploration well at the Puma West prospect in the deepwater US Gulf has yielded a significant oil discovery for operator BP. The well, on Green Canyon Block 821, was drilled using Seadrill drillship West Auriga to a total depth of 23,530 ft and encountered oil pay in a high-quality Miocene reservoir with fluid properties like productive Miocene reservoirs in the area. Preliminary data supports the potential for a commercial volume of hydrocarbons. The Puma West partners will begin planning an appraisal program to better define the discovered resource. The discovery well has been suspended as a keeper well to preserve future utility.
Abstract Gulf of Mexico (GOM) deep water has proven in recent years to be one of the most prolific oil production provinces in the world. The bulk of the new reserves and production to date in this area flow from subsalt, Miocene reservoirs at fields including Shenzi, Tahiti, Thunderhorse, and others (1). In the summer of 2005 Hess Corporation entered this arena and drilled the Green Canyon 468 ‘Pony’ discovery well. Information collected during subsequent appraisal drilling revealed significant insight into subsalt oil reservoirs which exist at depths between 28,000’ and 31,000’ TVD in this area. Geologic, reservoir engineering, facilities, and well construction studies have since resulted in a degree of clarity around the technical and economic viability of field development going forward. Of critical importance is addressing structural uncertainty below salt across Blocks 468 and 469. To reduce this uncertainty further appraisal drilling was approved late in 2009 on the eastern flank of the field. In addition to further structural and reservoir definition, Pony 3 objectives included a more robust casing design with deeper settings and larger diameter hole sections below salt to further confirm feasibility of future production wells. The 2010 program also included the utilization of a six generation dynamically positioned drill ship Stena Forth which provided a valuable advantage versus the single activity, moored semi-submersible utilized on earlier wells. Challenges inherent to ultra-deep wells in deepwater have been well documented in recent years (2, 3, 4, 5, 6). Hence, this paper will focus primarily on Pony well construction and deepwater field development planning. A number of key design issues will be highlighted including pore pressure/fracture gradient regression, casing design, bitumen (tar) mitigation, and salt creep mitigation. Incorporation of lessons learned and best practices from the substantial history of other deepwater operators has been a priority throughout this effort. Engineering and design in partnership with other operators is recognized as a critical element to ensure success in this challenging environment.