Lucky Mound Field: A New Mississippian Sherwood Shoreline Field

Abstract

Lucky Mound field produces oil and gas from the Sherwood interval of the Mississippian Mission Canyon Formation. Presently, eight wells are producing with development ongoing. Extensive coring, testing, logging, and petrographic evaluations throughout the field have allowed for detailed analysis of reservoir characteristics and paleoenvironmental interpretation. Sherwood shoreline fields typically produce from reservoir-quality packstones and grainstones trapped by a lateral facies changes into impermeable dolomite and anhydrite. At Lucky Mound, packstones, grainstones, and a productive dolomite facies all contribute to the producing interval. The productive dolomite facies is generally found in the upper portion of the Sherwood along the eastern margin of the field. Porosity as high as 22% and permeability values up to 16 md are present in the dolomite facies. These dolomites are the result of complete to partial replacement of micrite. In addition, the dolomitization process has enhanced intercrystalline and intraparticle porosity throughout the Sherwood interval. Pore types present include vuggy, intergranular, intraparticle, and intercrystalline. Pore occluding and replacive cements include fibrous calcite, prismatic calcite spar, baroque dolomite, anhydrite, celestite, pyrite, and chert. An understanding of carbonate depositional environments, diagenetic processes, Williston basin structural development, and Sherwood reservoir behavior is essential in the exploration for new Sherwoodmore » fields.« less