The history of hydrocarbon generation, expulsion and migration from the Upper Devonian Bakken and Mississippian Lodgepole source rocks in the Williston Basin has been successfully replicated by a 330-km long TEMISPACK model, running from the centre of Williston Basin to the Wapella oilfield in Saskatchewan. The model shows that oil generation is the cause of overpressures in the Bakken Fm., where shale vertical permeabilities must be as low as 10-2-10 -3 nD when overpressures are around 15 MPa. Hydraulic fracturing threshold was not commonly reached. Yet, our model suggests that expulsion efficiencies are as high as 0.85. Observed very low Bakken shale porosities (0.03) are entirely consistent with this result. They seem to account [...]
