Hydrogeology of the Bakken Formation Across the Williston Basin

Abstract

The Bakken Formation is currently the most productive oil producing formation in the entire Williston Basin and, one of the most productive tight oil plays in North America. This formation spans a large portion of the Williston Basin, and has been well documented as the most important petroleum source rock within the basin. Oil in the Bakken Formation has been shown to migrate from the central portion of the basin, which is currently in the oil window, outwards towards the less mature, portion of the basin and north to Canada. A clear understanding of the migration pathways is crucial for the further development of this formation; however, the influences and implications of groundwater flow on oil migration in the Bakken Formation remain unclear. Thus, this study focusses on expanding our hydrogeological knowledge of the Bakken Formation to determine how groundwater movement has influenced the accumulation of hydrocarbons within the formation. Pressure and chemistry data from both the Canadian and U.S. portions of the basin have been obtained from drill stem test reports and water analyses. These data were compiled into a database and culled to remove data affected by nearby production, injection or hydraulic fracturing operations. Up to date potentiometric surface maps, water driving force maps, and water chemistry distribution maps have been generated from the remaining data. Results show a large central area with greater than hydrostatic formation pressures. In distal areas of the basin, conditions return to near hydrostatic pressures. Production data has been combined with hydrogeological interpretations to identify an area within the Bakken Formation in which oil is the dominant mobile fluid. This area correlates with the mature portion of the basin which is currently undergoing active oil generation. Such areas might be preferentially targeted for further hydrocarbon exploration. This study provides the most complete depiction of the current flow regime in the Bakken Formation across the entire Williston Basin. Interpretation of these maps advances our understanding of the role that fluid movement plays in establishing the Bakken resource.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016