Pore-Scale Assessment of CO2 Solubility and Capillarity Trapping

Abstract Carbon Capture and Storage (CCS) has emerged as a pivotal technology in mitigating the escalating concern over anthropogenic CO2 emissions. This study undertakes a pore-scale investigation into the efficacy of CCS, emphasizing CO2 capillary and solubility trapping mechanisms within geological formations. Utilizing dynamic pore-scale imaging via x-ray micro-computed tomography (micro-CT), we examine the behavior of gaseous CO2 injected into water-saturated Idaho Gray sandstone under various flow rates. Our methodology involves a CT scan imaging through a flow cell, enabling precise control and observation of CO2 behavior during injection and imbibition processes. The research delineates the influence of injection rates on capillary trapping, revealing an optimal medium flow rate that maximizes CO2 retention within the pore network. Additionally, the study delves into the solubility dynamics of CO2 in response to pressure fluctuations, simulating real-world conditions of subsurface CO2 storage. Key findings suggest that injection rates play a critical role in trapping efficiency, with a 33.96% trapping efficiency observed at an intermediate rate of 0.05 ml/min. Moreover, the study captures the temporal evolution of CO2 solubility and exsolution, providing valuable insights into the long-term stability of sequestered CO2. By enhancing the understanding of CO2 phase behavior under varying reservoir conditions, this research offers significant contributions to the optimization of CCS strategies, with implications for both environmental sustainability and energy resource management.