Shale Wettability and Influencing Factors: A Statistical Investigation

Predicting the wetting behavior of shale rocks is important for understanding fluid flow in shales for CO2 geo-storage and enhanced oil recovery applications. However, shale rocks tend to demonstrate a much wider wettability variation compared to conventional rocks. Here, we present a new model for predicting advancing and receding contact angles for shale/CO2/brine systems. The model presented here considers shale wettability variation as a function of key influencing parameters including (a) operating conditions (i.e., pressure, temperature, and salinity), (b) shale total organic carbon (TOC), (c) thermal maturity, and (d) mineralogy of shale (including quartz, calcite, dolomite, clay, and pyrite content). The developed model shows that pressure and salinity are the most influencing parameters for both the advancing and receding contact angles. These are followed by temperature, TOC, and thermal maturity. The results of this study contribute toward predicting the wetting behavior of shale with known operating and functional properties and thus serve as an essential input in simulation models pertinent to flow behavior in shale rocks and therefore enhance hydrocarbon production from shales and CO2 storage in shale formations.