The lower Bakken / Exshaw interval has long been recognized as one of the richest source rocks for oil and gas in North America. While a mid-Bakken conventional sandstone play has been recognized and exploited in Canada since the mid-sixties, a new play in the tighter mid-Bakken siltstone has emerged as a result of technological developments in drilling and completion. Although in the last few years there has been great success exploiting the play, there still remain questions about the character of the reservoir, limits of the play, oil migration, and the relationship of the siltstone to other Bakken zones. This study attempts to answer these questions using an integrated geological, sedimentological, petrological, petrophysical and hydrogeological approach.