CO2 Leakage Into Shallow Aquifers: Modeling CO2 Gas Evolution and Accumulation at Interfaces of Heterogeneity

Abstract

Abstract In this work we conducted 1-D and 2-D simulations of CO2 flow and transport aimed at improving our fundamental understanding of processes associated with potential CO2 leakage into shallow aquifers resulting from carbon sequestration operations. In the 1-D simulations we optimized capillary pressure parameters and conducted sensitivity analysis to investigate the size of CO2 gas accumulation zones as the permeability in heterogeneous layers decreased. Our results indicate that accumulation zones do not necessarily increase as permeability decreases, and differences between capillary pressures for each layer play an important role. In the 2-D simulations we investigated the role of horizontal background flow, and its magnitude, on the formation of CO2 gas in the system. We showed that the formation of CO2 gas in the 2-D tank can be predicted with a simple 1-D expression when the horizontal background flow is not dominating the flow field near the leak. In addition, we showed that the location of the heterogeneous layer relative to the leak can have profound effects on the size and shape of the CO2 gas plume.