Completion Design for a Highly Compacting Deepwater Field

Abstract

Summary The Magnolia field, located in the deepwater region of the Gulf of Mexico, produces oil and gas from a tension leg platform (TLP) in 4,673 ft of water. The reservoirs comprise several stacked sandstone intervals within the early to mid Pleistocene with some minor production from the Miocene and Pliocene sands. A total of eight wells have been completed, with the majority of the production from the B25 sandstone. The formation-particle size is fine-grained sand to coarse silt and has relatively low K*H compared to other deepwater reservoirs. The reservoirs are significantly overpressured, highly compartmentalized, highly compacted, and have experienced significant pressure declines in excess of 8,000 psi in some cases during production. The wells were completed with cased-hole frac packs and each completion included a permanent downhole gauge, enabling interpretation of the K*H and skin throughout the producing history of the wells to date. The perforating guns, frac fluids, and screens were extensively tested before completion. The perforation-shot size and density was carefully chosen and tested to achieve the required production. Well test results matched inflow analysis predictions. The initial skin values generally met expectations and improved during production because of a combination of well cleanup and reduced reservoir permeability from compaction. Proppant integrity has been maintained under extreme depletion (>8,000 psi) conditions. Productivity was measured using perforation tunnel permeability (Kpt) analysis. The Kpt values were analyzed over the course of production and compared to similar type completions. The Kpt benchmark analysis shows that the completions are among the best in class. Well productivity has met or is above expectations, and the longevity has exceeded expectations in most cases.