Lucky Mound Field: A New Mississippian Sherwood Shoreline Field

FISHER, ROBERT W., Balcron Oil, Billings, MT, and MICHAEL L. HENDRICKS, Hendricks and Associates, Inc., Denver, CO

Lucky Mound field produces oil and gas from the Sherwood interval of the Mississippian Mission Canyon Formation. Lucky Mound was discovered in August 1990 with the completion of the Balcron Oil 33-15 Wahner, located in Sec. 15, T150N, R89W, McLean County, North Dakota. Lucky Mound is approximately 14 mi southwest of the Plaza/Wabek producing area and is one of the latest extensions of the Sherwood shoreline trend. 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 change 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 dol mitization 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 Sherwood fields.

AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)