The Bakken Formation of the Williston Basin is a prime example of an unconventionally produced petroleum system, with a low-permeability reservoir that requires application of advanced technologies for commercial production. A three-dimensional model of the Williston Basin was constructed to integrate and assess the parameters that influence the generation and migration of hydrocarbons in the Bakken Formation. This study tests the applicability of available basin and petroleum system modeling technology on an unusually low-permeability petroleum system.
The model is based on nine surfaces constructed from log tops of thousands of wells in the study area and additional depth and isopach maps of the Bakken Formation members. These were integrated with the established basin evolution in line with published research. Temperature and thermal maturity were calibrated during model construction from well temperature and geochemistry data. The resulting heat-flow map supports the existence of a heat-flow anomaly along longitude 103°W, discussed controversially in the literature. Furthermore, the results indicate that the invasion-percolation migration approach best describes the distribution of petroleum accumulation and the saturated areas in the Bakken members.
The volume of generated hydrocarbons was calculated, and the extent of the highly saturated accumulation beyond the area of the high-mature source was mapped. Furthermore, it was demonstrated that petroleum accumulations beyond the high-saturation zones have to be related to stratigraphic pinch-outs, lateral variability in permeability of the Bakken members, or smaller structural influences that were lost because of the resolution applied in the model.