Mini-review on the evaluation of thermodynamic parameters for surfactants adsorption onto rock reservoirs: cEOR applications

Abstract

Understanding thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) is crucial for characterizing surfactant adsorption mechanisms in chemical enhanced oil recovery (cEOR). This paper synthesizes recent studies on the thermodynamics of surfactant adsorption onto various reservoirs rock types, with a focus on quantitative and qualitative parameters critical to optimizing cEOR processes. Generally, surfactant adsorption is exothermic; for example, adsorption of sodium dodecyl sulfate and cetyltrimethylammonium bromide on sandstone and carbonate rocks yields ΔH° values between − 8 and − 20 kJ mol⁻¹ under typical reservoirs conditions. However, adsorption behaviors are influenced by factors such as surfactant type, rock mineralogy, salinity, and temperature, with occasional endothermic interactions observed in high-temperature reservoirs or with specific non-ionic surfactants. A positive linear correlation between ΔH° and ΔS° is commonly observed, indicating that increases in exothermic enthalpy (more negative ΔH°) are associated with increases in entropy (positive ΔS°), suggesting that adsorption processes that promote greater interfacial disorder are energetically favorable. This review not only consolidates key thermodynamic concepts but also provides a comparative analysis of thermodynamic parameters across different rock-surfactant systems, identifying trends and gaps in the literature. By offering insights into the specific conditions that enhance surfactant performance, this study establishes a thermodynamic framework to guide surfactant selection and optimization in cEOR. These contributions aim to deepen understanding of adsorption behavior and inform more effective, tailored cEOR strategies.