Regional Stratigraphic Analysis of the Three Forks Formation, Williston Basin, USA

The Three Forks Formation lies below the prolific Bakken Formation. It consists of sequences of arid subtidal to supratidal facies. The formation’s heterogeneous lithology ranges from mudstone to dolostone with varying amounts of evaporites. Depositional patterns have been greatly influenced by pre-existing structure and topography.

After deposition, complex and enigmatic diagenetic processes reshaped the character of the Three Forks Formation. Dolomitization, evaporite dissolution and re-precipitation, thermochemical sulfate reduction, and additional reduction by hydrocarbons are the major processes that effected reservoir quality.

Cores, petrographic thin sections, mineralogy, and core plug analysis data have been integrated to provide information on the potential of this formation as a petroleum reservoir in the western Williston Basin. The key to developing this reservoir lies within understanding the vertical and lateral facies distributions and their relationship to reservoir quality.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California