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Sedimentology and Reservoir Properties of the Three Forks Dolomite, Bakken Petroleum System, Williston Basin, U.S.A.

Ray Mitchell
Subsurface Technology, ConocoPhillips, Bartlesville, Oklahoma, USA

Although commonly referred to as part of the “shale gas revolution”, production from the Bakken Petroleum system is oil and mostly from interbedded carbonate intervals. The reservoir units include the Middle Bakken (a variety of siliciclastic and carbonate facies) and the Three Forks Formation (dolomite). The Upper and Lower Bakken Shales are the source rock and may also contribute to storage. Development of the light oil in these reservoirs is facilitated by long horizontal wells and multi-stage fracs.

The Three Forks Formation recovered in core commonly includes the upper Three Forks and partial recovery of the underlying middle Three Forks. Egenhoff et al (2011) identified 6 facies in the Three Forks; terrestrial paleosols, sabkha, subaerial gravity flows, intertidal, peritidal, and subtidal. Only the gravity flow, peritidal and sabkha deposits are common and widespread in the basin. Sabkha facies are not seen in the upper Three Forks cores in this study area.

AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012