Pore Connectivity Between Different Wettability Systems in Organic-Rich Shales

Pore connectivity controls fluid flow in porous media. Well-established methods such as permeability measurements or mercury-injection porosimetry are used to evaluate pore connectivity. However, these methods have limits in unconventional shale formation mainly because of the presence of different-wettability pores with large capillary pressures associated with them. In the present study, we have used the sequential spontaneous imbibition of brine and dodecane to study pore connectivity in shales. The present study shows the presence of water-wet pores, hydrocarbon-wet pores, and mixed-wettability pores. The water-wet pores are the continuous phase, and are controlled by the amount and distribution of inorganic water-wet minerals. The hydrocarbon-wet pores are essentially contained within the organic matter and require a minimum amount of total organic carbon (TOC), approximate to 3 wt%, to form a connected network of hydrocarbon wet pores. The approximate to 3 wt% of TOC is a necessary, but not sufficient, condition for developing connectivity throughout organic bodies. The mixed-wettability pores appear to enhance the systems connectivity.