Northern Montana east of the Rocky Mountains covers 63,000 sq mi (163,170 sq km). Excluding the areas unfavorable for oil production, 60,700 sq mi (157,210 sq km) and 96,000 cu mi (400,000 cu km) of sedimentary rocks are present. About 3 billion bbl of in-place oil has been discovered, and production is from all post-Cambrian systems except the Permian, Triassic, and Tertiary. It is estimated that approximately 1 billion bbl of in-place oil remains to be found. More than 500 million bbl of oil and nearly 450 billion cu ft of gas have been produced from this district. Seismic surveying for structural traps is the primary exploration tool in the Williston basin, and the search for stratigraphic traps is predominantly in the central and western areas. These methods will be c ntinued as long as success warrants their use.

The low density of drilling, multiple reservoirs, and variable stratigraphic conditions indicate that northern Montana has a good future potential.