Dependence of clay wettability on gas density

Understanding wettability of clay minerals is crucial in assessing primary migration of hydrocarbon and evaluating CO₂ storage capacities and containment security. In spite of recent efforts, there is considerable uncertainty of experimental data and theoretical predictions are lacking. We, therefore, developed new correlations to predict the advancing and receding contact angles of three different clay minerals (i.e., montmorillonite, Illite and kaolinite) as a function of gas density. To do so, we first measured clay minerals advancing and receding contact angles for helium, nitrogen, argon and carbon dioxide/brine systems at various pressures (5, 10, 15 and 20 MPa) and a constant temperature of 333 K. The statistical analysis shows that the developed correlations are capable of predicting the contact angles of the three clay minerals with very high accuracy (i.e., R > 0.95, for all the newly developed correlations). We thus conclude that the wettability of these clay minerals can be computed from knowledge of the gas densities, using these new empirical correlations. This work has important implications for improving wettability predictions, and thus reducing risks related to subsurface operations, such as CO₂ storage or hydrocarbon recovery.