An Overview of the Sappington Project With Implications for Future Generations of Bakken Reservoir Evaluations

Abstract

Since 2013 we have executed a phased outcrop program to study the Sappington formation, SW Montana, as an analog for the Bakken formation, Williston Basin, North Dakota. The Sappington formation is exposed in outcrops of the Central Montana Trough-fill. It is the exposed, chrono-stratigraphic equivalent (Devonian-Mississippian) of the subsurface Bakken formation and shares many geologic characteristics with the Middle Bakken reservoirs of the Williston basin. Both contain shallow marine, mixed siliciclastic and carbonate successions deposited in near-shore environments within shallow epeiric seas. The stratigraphic, sedimentologic and petrographic similarities between the formations are striking. The advantage provided by the Sappington outcrops is the information that can be obtained regarding the internal geometries and lateral continuity of sub-units and their constituent facies. This project has been executed in three phases. Phase 1 includes regional geologic investigations and establishment of a structural and stratigraphic framework for the Sappington formation. This work demonstrated the validity of the Sappington formation as an analog for the Bakken subsurface reservoirs. From this understanding, field sites were screened and selected for future phases of work. Priority was given to those exposures with lateral continuity approximating the scale of a Bakken Drill Spacing Unit (DSU). In Phase 2 we completed detailed studies of DSU-scale outcrops including acquisition of high-resolution digital terrain data (LiDAR) and geologic data from multiple, closely spaced sections. This information was used to create outcrop-based, geo-cellular reservoir models. These models were populated with Bakken reservoir data. Currently, in Phase 3 we have completed a behind-the-outcrop (BOC) coring and logging program and will update and revise the reservoir models with this new information. In future phases, insights gained though the Sappington project, integrated with Bakken data and used in conjunction with commercially available and proprietary technology will form the basis of approaches to; a) creating the next generation of Bakken reservoir models and depletion plans, and b) training future generations of Bakken geologists.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016