--> Bakken Oil-Generation Kinetics by Hydrous Pyrolysis and its Testing in 1-D Model
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Bakken Oil-Generation Kinetics by Hydrous Pyrolysis and its Testing in Previous Hit1-DTop Model

Abstract

The lower and upper Bakken shales are world class source rocks in the Williston Basin, sourcing reservoirs in the Bakken, upper Three Forks, and lower Lodgepole formations, which comprise the economically significant Bakken Petroleum System (BPS). A good understanding of the thermal-burial history of Bakken shales, with oil-generation kinetics as the key thermal dynamic parameter, is essential to achieve realistic charge history, which closely relates to Bakken oil presence in reservoirs of BPS across the Williston Basin. The maturation of immature Bakken shales under a hydrous closed-system setting was implemented by the method of hydrous pyrolysis (HP) in a temperature- and time-series. This method provides a conceivable analogue for natural oil generation and expulsion. The derived kinetics for Bakken shales includes activation energy at 53.79 kcal/mole and frequency factor at 1.25×1027m.y.-1 for an oil-generation reaction. These kinetic parameters were tested in a well constrained 1D thermal-burial history model. The modeled extent of oil generation correlates well with transformation ratios of Bakken shales from independent analysis. The HP oil-generation kinetics were also applied to other thermal-burial histories in the basin, and further modeling results indicate very minimal oil generation from Bakken shales in the Parshall Field and early oil generation in the Sanish Field. This agrees with measured thermal maturity indices and transformation ratios determined by atomic H/C ratios of isolated kerogens for those areas. The discovery of significant oil reserves in the Parshall/Sanish area suggests that, instead of charging from in-situ Bakken shales, the majority of discovered oil may have been laterally migrated from more mature down-dip Bakken shales adjacent to the Parshall/Sanish area.