Dataset for Integrated Petrophysical Analysis and 3-D Geological Model Development of the Bakken Unconventional Reservoir (Sanish Field)

billel Sennaoui, Kegang Ling, Prasad Pothana, Mojdeh Delshad

The Bakken Formation in the Williston Basin remains one of the most unconventional plays in North America, yet accurate reservoir characterization continues to be challenged by significant lithological heterogeneity, particularly within the Middle Bakken and Three Forks intervals. This study presents an integrated petrophysical analysis and 3-D geocellular model development for the Sanish field, covering approximately 157,060 acres in North Dakota. A comprehensive database comprising geophysical well logs from 100 wells, routine core analysis from 13 wells, and stratigraphic well tops was assembled to characterize the Upper, Middle, and Lower Bakken members and the Upper, Middle, and Lower Three Forks formations. Petrophysical properties, including shale volume, total and effective porosity, permeability, and water saturation, were estimated using neutron-density log methods and the modified Simandoux equation, with parameters calibrated against core measurements and validated through XRD and elemental capture spectroscopy data. Strong agreement was achieved between log-derived and core-measured properties in the Middle Bakken, while higher uncertainty persisted in the Three Forks owing to its complex dolostone-anhydrite mineralogy. Structural and stratigraphic surfaces were constructed using kriging interpolation, revealing average thicknesses of 14-24 ft for the Upper Bakken, 35-70 ft for the Middle Bakken, and 35-50 ft for the Lower Bakken, with the Three Forks intervals exhibiting greater
variability. A high-resolution geocellular grid (50 × 50 × 2.5 ft, 150 million cells) was populated using sequential Gaussian simulation to capture the spatial heterogeneity of reservoir properties. The resulting model provides a robust geological framework for subsequent reservoir simulation studies, including hydraulic fracture modeling, enhanced oil recovery evaluation, and CO₂ storage assessment in the Bakken unconventional system.