Influence of shale-total organic content on CO2 geo-storage potential

Shale CO2 wettability is a key factor which determines the structural trapping capacity of a caprock. However, the influence of shale-total organic content (TOC) on wettability (and thus on storage potential) has not been evaluated despite the fact that naturally occurring shale formations can vary dramatically in TOC, and that even minute TOC strongly affects storage capacities and containment security. Thus, there is a serious lack of understanding in terms of how shale, with varying organic content, performs in a CO2 geo-storage context. We demonstrate here that CO2-wettability scales with shale-TOC at storage conditions, and we propose that if TOC is low, shale is suitable as a caprock in conventional structural trapping scenarios, while if TOC is ultrahigh to medium, the shale itself is suitable as a storage medium (via adsorption trapping after CO2 injection through fractured horizontal wells).