Role of Natural Fracturing in Production from the Bakken Formation, Williston Basin, North Dakota
The Mississippian - Devonian Middle Bakken reservoir in the North Dakota portion of the Williston Basin is characterized by low matrix porosities (<8%) and permeabilities (<0.1 mD). For this reason natural fracturing is accredited as a key element responsible for the prolific oil production (>1000 BOPD initial well rates) from this reservoir. Integration of core, extensive borehole image analysis from horizontal wellbores, and petrophysical data have concluded that while natural fractures are present, they are probably not responsible for producibility. Natural fractures are generally lithologically-bound within a thin ‘brittle’ sequence within the Middle Bakken and have fracture heights constrained by bed thickness Limited permeability, connectivity, and spacing are inconsistent with the production rates. Other factors such as pore pressure, lithology, migration pathways and sealing capacity may actually be more relevant in understanding production variability as this play matures.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009