A resource evaluation of the Bakken Formation (Upper Devonian and Lower Mississippian) continuous oil accumulation, Williston Basin, North Dakota and Montana

The Upper Devonian and Lower Mississippian Bakken Formation in the United States portion of the Williston Basin is both the source and the reservoir for a continuous oil accumulation - in effect a single very large field - underlying approximately 17,800 mi2 (46,100 km2) of North Dakota and Montana. Within this area, the Bakken Formation continuous oil accumulation is not significantly influenced by the water column and cannot be analyzed in terms of conventional, discrete fields. Rather, the continuous accumulation can be envisioned as a collection of oil-charged cells, virtually all of which are capable of producing some oil, but which vary significantly in their production characteristics. Better wellperformance statistics are linked regionally to higher levels of thermal maturity and to lower levels of reservoir heterogeneity. Although portions of the Bakken Formation continuous oil accumulation have reached a mature stage of development, the accumulation as a whole is far from depleted.