Numerical and Experimental Study of the Kinetics of Permeability Changes in CO2-Saturated Brine Injection Process for Enhanced CO2 Sequestration

Injection of CO2-saturated brine into deep saline aquifers, one of the key components of carbon sequestration strategies, can significantly alter formation permeability through coupled geochemical reactions and fines migration. These changes can lead to either formation damage or stimulation, directly affecting injectivity and long-term storage performance and especially surface footprint. This study presents a comprehensive modeling and experimental approach to quantify the impact of mineral dissolution, precipitation, and fines migration during reactive, convective, and dispersive flow in sandstone reservoirs. A coupled numerical model integrates reactive transport equations with mineralogical kinetics, using saturation index calculations to predict dissolution and precipitation behavior. Permeability evolution is evaluated through the Kozeny–Carman relationship, while fines migration effects are incorporated using the Khilar and Fogler (1983) framework. Coreflood experiments under reservoir conditions were conducted for model development and validation. Two of the key elements of this process, the role of kaolinite and injection rate were further investigated by comparing numerical predictions and experimental outcomes across samples with various mineralogies. Post-injection diagnostics, including micro-CT imaging and geomechanical testing, provide insight into the physical drivers of permeability alteration. Results demonstrate that while conventional brine injection has a negligible impact, CO2-saturated brine (pH 3.2–4.4) can reduce permeability by up to 64%, with fines migration contributing more significantly than the impact of geochemical reactions. At low injection rates, however, fines migration becomes minimal. The presence of kaolinite mitigates permeability loss and, under certain conditions, enhances permeability due to its dissolution outweighing secondary mineral precipitation. This study provides critical insights into optimizing CO2-saturated brine injection by tailoring brine composition and injection strategies to minimize formation damage. Understanding permeability evolution during this process and the key parameters are essential for predicting near-wellbore behavior, maintaining injectivity, and improving the overall efficiency of carbon storage projects.