Advances and challenges in CO2 foam technologies for enhanced oil recovery in carbonate reservoirs

The use of surfactants for foam generation and gas-mobility control to improve oil recovery of CO2 flooding processes has been extensively studied. This review covers the most important aspects regarding the design of CO2-foams for mobility control in carbonate reservoirs, including recent advances in the formulation of novel surfactants, analytical techniques to determine key properties such as adsorption and thermal stability, and bench-scale visualization systems of foam flow. Several key concepts regarding foam transport in porous media are reviewed such as the minimum pressure gradient, the effect of the partition coefficient for CO2-soluble surfactants, and the effect of oil on foam stability and rheology. This work also discusses the most recent advances of two major foam modeling methods, the semi-empirical STARS foam model and the population balance model, along with recent CO2 foam pilot tests and the elements governing success in foam deployment and oil recovery.