Numerical simulation of porosity and permeability evolution of Mount Simon sandstone under geological carbon sequestration conditions

- A model is developed to simulate reactions between Mount Simon sandstone and CO2 under CO2 storage conditions.
- A model predicts 50% permeability decrease of sandstone after 6-month exposure to CO2, which is consistent with lab results.
- Siderite (FeCO3) precipitation is the primary contributor to permeability decrease.
- Permeability reduction of host rock may improve lateral containment of CO2, contributing to overall security of CO2 storage.

A numerical model was developed with the use of reactive transport code CrunchFlow to estimate porosity, permeability and mineral composition changes of Mount Simon sandstone under typical geological carbon sequestration conditions (P = 23.8 MPa and T = 85 °C). The model predicted a permeability decrease from 1.60 mD to 1.02 mD for the Mount Simon sandstone sample in a static batch reactor after 180 days of exposure to CO2-saturated brine, which is consistent with measured permeability results. Model-predicted solution chemistry results were also consistent with laboratory-measured solution chemistry data. SiO2 (am) was the primary mineral that causes permeability decrease, followed by kaolinite. Both SiO2 (am) formation and kaolinite formation were attributed to the dissolution of quartz and feldspar. This study shows that the formation of SiO2 (am) and kaolinite in the pore space of host rock is possible under typical CO2 sequestration conditions. SiO2 (am) and kaolinite precipitation at the CO2 plume extent could reduce the permeability of host rock and improve lateral containment of free-phase CO2, contributing to overall security of CO2 storage.