--> Beyond the Bakken, an Integrated Evaluation of Williston Basin Lodgepole/Mission Canyon, Bakken and Ordovician Petroleum Systems

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Beyond the Bakken, an Integrated Evaluation of Williston Basin Lodgepole/Mission Canyon, Bakken and Ordovician Petroleum Systems

Abstract

While the Bakken petroleum system (along with the Eagle Ford of Texas) is an established success – with both plays anecdotally displacing in excess of 2.0MM Bbl of imported oil/day, there are other opportunities for resource plays within Williston basin source rock horizons. Hydrocarbon molecular and isotopic data were integrated with source rock data to yield new insight into the Ordovician Red River and Mississippian Lodgepole/Mission Canyon petroleum systems of the Williston Basin as future resource plays and to provide greater details of the Bakken system. Using multivariate statistics, over 350 Williston Basin oils were grouped into seven families which share common sources based on genetic-specific terpane and sterane biomarkers and stable carbon isotope compositions. Ninety (90) Middle Ordovician-sourced oils were identified by their unique n-paraffin distributions due to the microorganism G. prisca, as well as having the most positive (enriched) stable carbon isotope compositions of oils from the Williston Basin. Most of these oils were produced from the Ordovician Red River Formation, and source rock evaluation of Red River cores and cuttings suggests that the Red River is also the principal source rock unit. Furthermore, another smaller set of oils contain G. prisca biomarkers but have very negative (depleted) stable carbon isotopic compositions; these oils may have been generated from shales of the Ordovician Winnipeg Group. Similarly, genetic-specific biomarker ratios and carbon isotopes of Williston Basin produced oils were used to identify three oil families derived from Mississippian carbonate source rocks. Families 2 and 3 were derived from distinct facies; Family 1 is a mixture of 2 & 3 or 2 and a Bakken input. These carbonate families differ due to algal sterane distributions and stable carbon isotopic compositions. A subset of Red River oils have mixed with Lodgepole oils. Multiple Bakken oil subfamilies were distinguished in the study, including distinct subfamilies in Montana's Elm Coulee Field, Parshall Field and Three Forks-reservoired oils. Relative contributions of Upper and Lower Bakken source units to Middle Bakken and Three Forks production were delineated. Vitrinite reflectance equivalent values (VRE) were calculated for each of the oils in the study. This allowed prediction of in-place and migrated oil occurrences for all three petroleum systems.