Effect of spatial heterogeneity on plume distribution and dilution during CO2 sequestration

Storage in deep saline aquifers is one of the major options for sequestering carbon dioxide. This paper presents the results of modeling long-term CO2 storage in a deep saline aquifer with a reservoir simulator. The objective is to investigate the effect of aquifer heterogeneity on plume migration and dilution with Monte Carlo simulation. We focus on the first and second spatial moments of the plume and the dilution index for various reservoir parameters, including the average permeability, the vertical to horizontal permeability ratio (kv/kh), and the variance and correlation length ratio of heterogeneity. A relative dispersion framework used to analyze the Monte Carlo simulations gives a more reasonable estimation of the plume distribution, dilution index, and spatial moments than does the commonly used absolute dispersion framework. The impact of the injection completion interval and its location is also studied. It is found that the medium spatial heterogeneity and the choice of the completion interval for CO2 injection have a significant effect on plume distribution and dilution of CO2.