Summary

Sappington Formation outcrops of the Central Montana Trough are being developed as a reservoir analog for the subsurface Bakken Formation of the Williston Basin. Correlations utilizing sequence stratigraphy, biostratigraphy (conodonts, palynomorphs, and acritarchs), and geochemistry link the two noncontiguous sections across the intervening Central Montana Arch where the section is not present. These correlations indicate that the variably sandy Middle Sappington siltstone succession (units 2, 3, 4 and 5) is directly comparable to the likewise sandy siltstones of the Middle Bakken. A similar succession of facies allows the complex lateral and vertical heterogeneity that characterizes the subsurface reservoir to be visualized and studied. Although not directly comparable, the overall similar depositional setting and generally similar facies also allows the analog to be extended to the upper parts of the Middle Bakken. Conversely, another key learning is that the Three Forks Formation underlying the Sappington is not a direct analog for the Three Forks reservoirs of the Williston Basin. Similarities extend however to the Saskatchewan part of the Williston Basin and the Alberta Bakken.

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