An evaluation of the hydrocarbon potential of the proposed Great Bear Wilderness Area, Flathead, Teton, and Pondera counties, Montana

The proposed Great Bear wilderness study area has very good potential for discovery of natural gas resources and somewhat lesser potential for oil production. The area contains numerous potential hydrocarbon reservoir and source rocks. Structural traps for the accumulation of gas in the subsurface cannot be determined without seismic surveys and possibly drill holes, but structural traps can be inferred from a comparison of the surface geology of the study area with that in gas producing areas to the north in Alberta, Canada. The proposed wilderness study area is in the northern disturbed belt of Montana which contains a structural and stratigraphic history similar to that in the Alberta disturbed belt which contains major reserves of gas and minor amounts of oil. Successful gas exploration has been conducted a few miles east of the study area, but no seismic or drilling operations have been conducted within the area. Five wells east of the area were drilled in the 1950's. All these wells recovered natural gas but were shut-in, or abandoned, because the region was too remote and the price of gas too low for profitable production. These wells had a total potential productive capacity of 6.3 million cubic feet ofmore » gas per day. The area contains potential hydrocarbon reservoir rocks of Devonian, Mississippian, Jurassic, and Lower Cretaceous ages of which most of them produce oil and/or gas from fields to the east on the Sweetgrass Arch. Some of the potential reservoir units thicken markedly within the study area. All potential reservoir units are overlain by shale, a common cap-rock for hydrocarbons.« less