Effects of SiO<sub>2</sub> Nanoparticles on Wettability and CO<sub>2</sub>–Brine–Rock Interactions in Carbonate Reservoirs: Implications for CO<sub>2</sub> Storage
Yongsheng Tan, Qi Li, Liang Xu, Chikezie Chimere Onyekwena, Tao Yu, Lifeng Xu
Abstract
Nanoparticles effectively enhance the CO 2 geological storage capacity by altering wettability during CO 2 –brine–rock interactions, which significantly impacts the CO 2 residual trapping and migration in reservoirs. However, the effect of nanoparticles on CO 2 –brine–rock interactions in carbonate formations is poorly understood. Therefore, in this study, the impact of SiO 2 nanoparticles (SNPs) on CO 2 –brine–rock interactions was evaluated under supercritical CO 2 conditions (60 °C and 12 MPa) by analyzing wettability, conducting X-ray diffraction, scanning electron microscopy analyses, measuring weight loss, and performing low-field nuclear magnetic resonance (LFNMR) tests. The results indicated that (a) both CO 2 –brine–rock interactions and SNPs–CO 2 –brine–rock interactions can alter the wettability of carbonate rock surfaces from oil-wet to water-wet and that the carbonate rock became more water-wet after SNPs addition; (b) CO 2 –brine–rock interactions primarily involved the dissolution of calcite in carbonate rocks under acidic conditions, but SNPs–CO 2 –brine–rock interactions were more intense; (c) based on LFNMR analysis, the pores of the carbonate core in this study were divided into small pores ( T 2 < 5 ms) and large pores ( T 2 > 5 ms), with CO 2 –brine–rock interactions occurring mainly in the large pores of the carbonate cores but with enhanced interactions in small pores; (d) CO 2 solubility in solution after CO 2 –brine–rock interactions increased with increasing pressure and eventually reached equilibrium, and this trend was observed both in the CO 2 –brine–rock system and the SNPs–CO 2 –brine–rock system. However, the CO 2 solubility in the SNPs–CO 2 –brine–rock system was greater than that in the CO 2 –brine–rock system.