Viscosification of CO2 to improve subsurface storage — A modeling study

Abstract

In this work, we numerically investigate the potential benefits of a recently proposed functional molecule that can both significantly increase the viscosity of CO2 and reduce the residual water saturation in the context of CO2 storage in subsurface aquifers. We model different degrees of CO2 viscosification in field-scale formations at both shallow and greater depths, consider a range of permeabilities from 100 md to 2,000 md, and both homogeneous and highly heterogeneous formations. To quantify the impacts of CO2 viscosification, we track multiple domain-integrated quantitative measures such as CO2 tip velocity and dispersion widths. In all scenarios, we find that CO2 viscosification increases the total amount of CO2 retained but the degree of improvement varies. Moreover, the fraction of solubility trapping versus structural trapping is highest for neat CO2. These modeling results can inform stakeholders in CO2 viscosification technology for future large-scale CO2 storage projects.