SDS-Modified Silica Aerogels: Investigating Wettability Alteration in Carbonate Saline Aquifers for Potential CO2 Sequestration Applications

Wettability alteration is a promising strategy to enhance CO 2 containment in geological storage by modifying rock-fluid interactions. This study synthesized and optimized sodium dodecyl sulfate-modified silica aerogel (SDS-SA) nanoparticles to achieve controlled alteration of wettability in carbonate rock under saline aquifer conditions. SA was prepared using a sol–gel method and subsequently surface-modified with SDS. Response surface methodology (RSM) was used to model and optimize the wettability-altering process, with SDS/SA ratio, nanoparticle concentration, and pressure as independent variables. Experiments were performed at 50 °C in synthetic brine (40,000 ppm NaCl and 500 ppm MgCl 2 ). The optimized nanofluid shifted carbonate slices from weakly CO 2 -wet to moderately water-wet, reducing the CO 2 –brine–rock average contact angle from 80.01° to 53.22°, thereby providing a tunable parameter for probing interfacial influences on storage processes. The modified nanoparticles exhibited enhanced colloidal stability, with a negative zeta potential and without aggregation observed for more than 500 hours in the optimized divalent-ion brine (40,000 ppm NaCl + 500 ppm MgCl 2 ) under static laboratory conditions: temperature = 50 °C, ambient pressure (∼1 bar), sealed vials with no agitation. Successful surface modification and nanoparticle adhesion were confirmed through BET, FESEM, EDS, and FTIR analyses. Overall, the stable, tunable nanofluid platform integrated with RSM-based optimization provides a promising approach for controlled wettability alteration in static experiments, laying the groundwork for future investigations into the influence of engineered interfacial properties on multiphase flow and CO 2 sequestration mechanisms at reservoir-relevant scales. It should be noted that the present study focuses on static wettability measurements and nanoparticle stability evaluation. The implications for CO 2 storage are discussed qualitatively, while further validation through dynamic core-flooding experiments is required to quantify the impact on CO 2 trapping efficiency.