Montana & North Dakota
April 30, 1996

The presence of a dynamic water flow field in the Williston Basin has been documented by a number of studies published in the literature. Our investigation shows that hydrodynamic gradients and water flow commenced during Laramide uplift coinciding with peak oil expulsion. Thus hydrocarbon migration in regional aquifers has been strongly influenced by water flow. A very compelling reason for conducting a basin wide hydrodynamic study is to determine the potential migration direction of both Bakken- and Yeomen-sourced oils. The Williston Basin Hydrogeology study evaluates 17 reservoir zones from Upper Cretaceous to the Cambrian and includes data from Saskatchewan, Manitoba, North Dakota and Montana. Phase I focuses on pressure continuity and shows. Phase II focuses on the definition of source rock maturity zones and provides analysis of oil migration patterns for all major reservoirs. Phase III focuses on Thematic Studies (e.g., shallow gas). In Phase I of this study, the objective is to systematically map the hydrogeology of all major producing horizons in the U.S. portion of the Williston Basin. Specific objectives and application of the study are: • Determine fluid flow patterns in all major reservoirs in the study area • Determine the salinity distribution • Determine the hydraulic head distribution • Determine the affect of fluid flow on hydrocarbon migration • Identify areas of hydraulic continuity and significant hydraulic breaks, and their impact on hydrocarbon entrapment • Identify potential fairways that affect hydrocarbon migration and entrapment • Provide basis for calculating minimum structural closures required for entrapment • Construct selected pressure/depth, pressure/elevation plots for the purpose of verifying hydraulic breaks and conducting static gradient analysis

Montana & North Dakota
T18-37N, R35-60E, T144-163N, R70-105W