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From core-scale experiment to reservoir-scale modeling: A scale-up approach to investigate reaction-induced permeability evolution of CO2 storage reservoir and caprock at a U.S. CO2 storage site

Wang, Yan, Zhang, Liwei, Soong, Yee, Dilmore, Robert, Liu, Hejuan, Lei, Hongwu, Li, Xiaochun
Computers & geosciences 2019 v.125 pp. 55-68
carbon dioxide, carbon dioxide production, computers, minerals, models, pH, permeability, porosity, silica, Mississippi
Mineral dissolution and secondary mineral precipitation can cause porosity and permeability changes of CO2 storage reservoirs and caprocks after injection of CO2. In this paper, a 3-step approach (core-scale experiment →core-scale modeling →reservoir-scale modeling) is developed to simulate reservoir-scale porosity and permeability evolution of CO2 storage formation and caprock at a model CO2 storage site. The model site is based on characteristics of a real site in Mississippi, USA. Important chemical and permeability modeling parameters in the reservoir-scale model are validated by core-scale experimental and reactive transport modeling results. The reservoir-scale model predicts a maximum 3.2% permeability increase of the CO2 storage formation and a maximum 1.1% permeability increase of the caprock after 1000 years of exposure to CO2-rich brine, while the core-scale model predicts 7% permeability decrease for a small CO2 storage formation core and 296% permeability increase for a small caprock core after 180-day exposure to CO2-rich brine. The discrepancy between permeability results of reservoir-scale model and core-scale model is attributed to strong pH buffering effect of CO2 storage formation with large mass of H+-consuming minerals. Therefore, using core-scale experiments/models only is not sufficient to elucidate reservoir-scale permeability evolution. Variations of key model parameters have a small effect on permeability evolution of both CO2 storage formation and caprock, except for variations of Keq (SiO2 (am)) and the exponent n in permeability-porosity correlation. SiO2 (am) is a key mineral that governs permeability evolution of CO2 storage formation and caprock, given the characteristics of the model CO2 storage site.