Evaluation of Impacts of Permeability and Porosity of Storage Formations on Leakage Risk of Deep Groundwater and Carbon Dioxide Due to Geologic Carbon Dioxide Storage

Abstract:

A series of analysis modeling was performed using a behavior prediction model and a leakage risk analysis model to evaluate quantitatively impacts of hydrogeologic properties (intrinsic permeability and porosity) of storage formations (reservoir rocks) on leakage risk of deep groundwater (brine) and carbon dioxide (CO₂) due to geologic CO₂ storage. In this study, an abandoned well and a fault are considered as leakage pathways for deep groundwater and CO₂ leakage from a storage formation into an overlying near-surface aquifer. A series of prediction modeling of behavior of deep groundwater and CO₂ in the storage formation was performed first using a behavior prediction model TOUGH2 (Pruess et al., 1999, 2012) to obtain spatial and temporal distributions of the pressure, temperature, and saturation of deep groundwater and CO₂ as well as the mass fraction (solubility) of CO₂ in deep groundwater along the upper boundary of the storage formation beneath the overlying cap rock. These spatial and temporal distributions are used as input data in the next leakage risk analysis modeling. A series of analysis modeling of leakage risk of deep groundwater and CO₂ through either the abandoned well or the fault was then performed using a leakage risk analysis model CO₂-LEAK (Kim, 2012). The analysis modeling results show that CO₂ injection can cause deep groundwater (brine) and CO₂ (both free fluid and aqueous phases) leakage into the overlying near-surface aquifer through either the abandoned well or the fault. In that case, brine leaks first, aqueous phase of CO₂ then leaks, and free fluid phase of CO₂ leaks finally, whereas their leakage rates and amounts through the fault is much greater than those through the abandoned well. The analysis modeling results also reveal that the leakage rate and amount of deep groundwater are almost independent of permeability and porosity of the storage formation. However, the leakage rate and amount of CO₂ are dependent on and inversely proportional to them. In addition, the leakage rate and amount of CO₂ are more sensitive to permeability than porosity of the storage formation. This work was supported by the Geo-Advanced Innovative Action (GAIA) Program funded by the Korea Environmental Industry and Technology Institute (KEITI), Ministry of Environment, Republic of Korea.