Geochemical Modeling and Microfluidic Experiments To Analyze Impact of Clay Type and Cations on Low-Salinity Water Flooding

The types of clay minerals and cations are the factors controlling improved recovery from low-salinity water (LSW) injection. In this paper, a surface complexation model was developed to predict the clay surface charge that develops for different brine compositions and salinities. It was followed by microfluidic experiments to visualize the individual performances of illite, kaolinite, and brine compositions and salinities during LSW injection. An automated measurement was conducted using an algorithm that determines contact angles from pore-space images. Our model results were substantiated against microfluidic observations. Based on the observations coupled with the simulation results, it is concluded that in kaolinite as an edge-chargedominated clay, the charge development is significant under differing pH and ionic strengths. Accordingly, it responded well to LSW in the system under study, whereas illite as a basal-charged clay did not. This could elucidate the unlike sensitivities of clays to LSW, which in turn leads to different extents of wettability alteration.