173-10 Depositional Facies Controls in a Hydrocarbon-Producing Mixed Siliciclastic–Carbonate System within an Intracratonic Basin: Middle Member of the Bakken Formation, Williston Basin, North Dakota, USA.

Session: Geologic Energy Resources and Storage for Now and the Future

Presenting Author:

Authors:

Abstract:

Hydrocarbon-bearing basins—whether formed in compressional settings, influenced by salt tectonics, or considered tectonically quiescent intracratonic systems—require site-specific stratigraphic analysis due to potential facies variability. This is particularly critical in intracratonic basins where stratigraphic traps dominate production, as even short-distance facies shifts can significantly impact reservoir continuity and performance. The middle member of the Bakken Formation in the Williston Basin exemplifies such complexity, contributing approximately 93% of North Dakota’s 1.1 million barrels of daily oil production.

Vertical facies successions and depositional processes of the Middle Bakken—deposited on a low-gradient, tropical intracratonic ramp during the late Devonian to early Mississippian—were investigated using data from over 70 hydrocarbon wells, including 24 slabbed cores and 52 thin sections. Fifteen individual facies were identified and grouped into four distinct facies associations that reflect deposition under varying energy regimes governed by fair-weather and storm-wave–induced bottom currents. Two vertical successions were recognized: (1) a localized carbonate-dominated interval and (2) a more widespread, basin-scale mixed siliciclastic–carbonate succession. Inherited structural weaknesses within the Precambrian basement exerted a first-order control on long-term subsidence patterns, producing subtle paleo-bathymetric highs. These highs influenced sediment distribution and depositional processes and promoted early diagenesis during calm intervals following storm activity, further complicating lateral reservoir predictability.

Even so-called tectonically quiescent intracratonic basins can exhibit subtle tectonic influences, whether via basement reactivation or sediment-load–driven differential subsidence. These influences manifest as lateral facies heterogeneity, emphasizing the need for high-resolution, site-specific analysis in hydrocarbon exploration, development, and CO₂ EOR implementation. The integrative approach outlined here may serve as a model for stratigraphic and structural interpretation in other intracratonic hydrocarbon systems globally.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5937

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.