Insights into mechanism of wettability alteration caused by CO2-brine-rock interactions from interfacial features of brine-rock viainter molecular forces

Abstract

Wettability is a significant attribute in CO2 geosequestration and CO2 Enhanced Oil Recovery (CO2-EOR) operations, and affects the transport law, capture capacity, sealing capacity and leakage possibility of supercritical CO2 in tight sandstone reservoirs. However, the supercritical CO2-brine-rock reaction leads to wettability alteration of tight sandstone, and the mechanism remains unclear. In this paper, Zeta potential measurement, Fourier Transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used to characterize the surface properties of tight sandstone. Results show that with the increase of reaction time, the mineral composition of tight sandstone changes, the absolute value of zeta potential decreases, the electrostatic force decreases, but the content of hydrophilic uncharged groups increases, the van der Waals force and hydrogen bond force increase, and finally the hydrophilicity increases.