The Exshaw Formation consists of a lower black shale member (equivalent to the lower Bakken shale in Saskatchewan and the Williston Basin) and an upper siltstone member (equivalent to the middle Bakken sand / siltstone). Overlying the siltstone is a black shale of the Banff Formation (equivalent to the upper Bakken shale).
The Exshaw, although widespread, has two limitations:
1. A significant portion of the formation did not reach hydrocarbon-generating maturity levels.
2. Overall, it is very thin compared to other shale plays.
Notwithstanding the typically thin nature of the Exshaw shale, the richness of the source rock and known hydrocarbon generation implies that significant amounts of oil and/or gas may be reservoired in the Exshaw siltstone and the adjacent Wabamun and Banff formations. These potential reservoirs may be either conventional or unconventional, depending on local porosity and permeability.
Based on Rock Eval data, there are three significant regional areas that warrant more detailed work:
1. Southwest Alberta.
2. South side of the Peace River Arch.
3. Desan area (east of the Bovie-Maxhamish Fault).
All three have a high oil-prospectivity potential. Gas prospectivity is not quite as strong and, naturally, is more westerly and deeper than the oil-prone areas.