This paper discusses the methodology necessary for lithology identification and petrophysical analysis of an unconventional reservoir in Williston Basin. The scope of the work is done on a producing oilfield in the North Dakota portion of the basin. Well logs from 45 wells in Blue Buttes Field were analyzed, mainly focusing on the Middle Bakken section of the Bakken Formation. Reservoir properties, such as permeability, effective porosity, shale volume, and saturation were determined using a set of commercial software. Several methods for analyzing each property were tried, the results were compared and the best method was picked that matched the core analysis such as the XRD scanning.

The results of this study can help with a decision regarding the further development of the reservoir specifically in the Blue Buttes Field or to improve the understanding of various properties from the Middle Bakken. The procedures presented in this paper will help to establish a workflow for similar studies in other unconventional reservoirs in the future. This case study also helps better understand the lithology and rock properties of the Middle Bakken.

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