Porosity development in the Mississippian pisolitic limestones of the Mission Canyon formation, Glenburn field, Williston basin, North Dakota.

Abstract

Limestones of the Frobisher-Alida zone of the upper Mission canyon produce hydrocarbons in the Glenburn field from porosity largely developed through subaerial diagenetic processes. Vadose pisolites, carbonate crusts and solution features are major fabrics in cores of the pay zone. The development of porosity was in part coeval with anhydrite deposition in pans or supratidal sabkhas on the flanks of a very low topographic arch. Flank salt-solution or ancestral structural development are plausible mechanisms for construction of limestone prominences. Dolomitization along the flanks, coupled with minute interbeds of anhydrite, support contemporaneous porosity development and evaporite deposition. Early cementation was followed by the formation of vadose pisolite and other solution/desiccation features. The vadose pisolite may have been partly contemporaneous with early cementation. The last major diagenetic phase was intrastratal solution. Porosity is lenticular in part. The oil-water contact is probably an irregular surface because of varying pore dimensions.-J.M.H.