Development and Application of a Multi-scale, Multi-layer Numerical Model for CO2 Injection

Abstract

Geologic sequestration of carbon dioxide (CO2) in deep saline aquifers is a proposed greenhouse gas mitigation technology with potential to signi ficantly reduce atmospheric emissions of CO2 from large, stationary point sources such as fossil fuel burning power plants. Feasibility assessments of proposed sequestration sites require realistic, computationally efficient models to simulate the subsurface pressure response and quantify the risks of leakage. Such basin-scale models must also be able to capture important features of the system on smaller length scales, and a new analytical subscale correction for calculating the pressures at injection wells is developed to preserve finer-scale resolution without sacri ficing efficiency. Diffuse flows of brine through the low-permeability aquitards between the aquifers may signi ficantly influence the pressure response, necessitating a multi-layer model. The impacts of di ffuse leakage are investigated for a proposed sequestration site in Canada using a quasi three-dimensional model that accounts for transient aquitard flows. The modeling results show reductions in both the maximum subsurface pressure buildup and the spatial extent of the pressure perturbation due to injection with increasing aquitard permeability, though the magnitudes of these eff ects depend also on aquifer properties.