INTEGRATED CHARACTERIZATION OF THE LOWER BAKKEN SHALE, DIVIDE COUNTY, NORTH DAKOTA

The Lower Bakken Shale is an essential member of the Bakken Petroleum System, which is a prolific unconventional accumulation in North America. The unconventional accumulations are sometimes faced with the challenges of unpredictable lateral variation in hydrocarbon production due to variety of some rock properties. Therefore, understanding the source rock potential, mineralogy and petrophysical properties of this unit is essential in characterizing the hydrocarbon potential of the Lower Bakken Shale around any specific study area.

This study utilized cores from four wells within three fields in Divide County of North Dakota. Samples were collected for Rock Eval pyrolysis, petrographic thin section studies, XRD bulk mineralogy, Scanning Electron Microscopy (SEM) analysis, porosity and pore fluids distributions. The helium porosimetry and NMR T2 porosity techniques were both used to estimate porosity, this was designed to quality check the results and avoid discrepancies.

Results showed that the Lower Bakken shale in Divide county have varying maturity from immature to mature using a 435°C maturity benchmark. The mineralogic components were grouped into major and accessory minerals based on composition percentages. Various pores types and internal constituents were identified and described through SEM analysis. Porosity values vary for both methodologies utilized but differences were minimal. Clay bound water was identified to be the dominant fluid within the shales using the T2 cutoff values and supporting evidence from the abundance of clay matrix porosity.