A numerical study to assess the effect of heterogeneity on CO2 storage potential of saline aquifers

Abstract

Many parameters have been indicated crucial for the selection of a saline aquifer as a carbon dioxide (CO2) storage site. However, less attention has been given to the impact of heterogeneity on the performance of these storage media. Thus, the heterogeneity effect was evaluated in this paper by adopting a numerical modeling approach and the existing screening criterion developed for the aquifers was updated. The updated criterion for CO2 storage purpose would enhance the confidence level during the selection of deep saline aquifer and thus, help to address the climate change issue. The numerical modeling was carried out via CO2STORE module of Eclipse300 Simulator to evaluate the effect of different levels of heterogeneity on CO2 storage potential. Different degrees of heterogeneity from homogenous systems to highly heterogeneous systems in the model were incorporated through the Lorenz coefficient. In this way, simulation of nine cases was carried out for three different aquifers with different porosity values. A comparison of these results showed that heterogeneity causes the aquifer to have lower storage capacity. On the trapping potential, dissolution trapping was significant and the amount of free gas in all cases was minimum. In addition, the aquifer with the highest level of heterogeneity (HLH) had a minimum fraction of residual trapping regardless of porosity. It was also found that final pressure at the end of 30 years is the same and high for low-level heterogeneity (LLH) and medium level heterogeneity (MLH) cases and low for HLH, while the injection rate stability duration is least for HLH and maximum for LLH. Based on the results obtained, it can be concluded that low to medium level heterogeneous aquifers with a good porosity can be a suitable choice for CO2 storage.