Modeling the optimal foam injection slug in porous medium accounting adsorption effects

Abstract

This study addresses the optimization of surfactant slug design for foam injection in porous media, focusing on applications relevant to carbon capture and storage (CCS) and carbon capture, utilization, and storage (CCUS). We describe the foam flow in a one-dimensional porous medium as a sequence of two Riemann problems, explicitly accounting for surfactant adsorption on the rock surface impacting the surfactant mass available for foam generation. Utilizing the modified implicit texture foam model from the commercial simulator CMG/STARS, we extended previous Riemann problem solutions to include more realistic modeling. Following the classical definition of optimal slug size, we propose a methodology to minimize surfactant usage while maximizing carbon dioxide storage efficiency. The resulting Pareto front offers valuable insights for practical applications. Our key findings indicate a strong dependence of optimal slug properties on adsorption parameters, underscoring the importance of accurately modeling reservoir rock surface — surfactant interactions. Despite employing the linear Henry adsorption isotherm, the identified optimal surfactant concentrations are primarily low, corresponding to the parameter range where this model is physically accurate, supporting our approach. Additionally, Pareto front analysis suggests a methodology to investigate the economic potential of the foam injection. All analytical solutions were validated through direct numerical simulations.