Effect of anionic surfactant on interfacial tension and wettability of rock/water/CO2 system under geological carbon storage conditions

Abstract

Over the last decades, geological carbon storage (GCS) has emerged as an essential strategy to sequester or store captured carbon dioxide (CO$_2$). The GCS strategy involves the injection of CO$_2$ into deep geological formations and its ensuing storage within a porous media, where the interfacial tension (IFT) between CO$_2$ and indigenous pore fluids, as well as the contact angle (CA), governs the efficiency of CO$_2$ storage. This study focuses on enhancing CO$_2$ storage efficiency by reducing the capillary factor through the alteration of the IFT and CA using Sodium Dodecyl Sulfate (SDS), an anionic surfactant, and quartz, Mancos shale, and Berea sandstone as the surfaces to determine CA. High-pressure and high-temperature experiments were conducted in the range of 1-12 MPa and 25-80°C, employing techniques such as pendant and rising drop for IFT measurement and sessile and tilting plate for CA analysis. Results show that at 40°C, the IFT reduces by 10.5 mN/m (59% decrease) at 10 MPa, with an estimated critical micelle concentration (CMC) of approximately 60% of the original CMC. At 80°C, the IFT decreases by 47% at 10 MPa, with a CMC of around 70% of the original value. Continuing with the CA, all the substrates are originally water-wet exhibiting values of static CA between 19° and 28°, with a slight increase in CA when increasing pressure and negligible effect of temperature. Dynamic angles (i.e., advancing and receding angles) of Mancos shale and Berea sandstone show a similar trend, contrary to the experimental results corresponding to the quartz substrates. After the addition of SDS, the three substrates show a more water-wet state, being the quartz samples the most affected. When computing the capillary factor, SDS shows its capability to enhance the injection and storage of CO$_2$, quantified through the sweep efficiency going from 27% to 39% at the point of maximum reduction of the capillary factor.