Predicting microemulsion phase behavior using physics based HLD-NAC equation of state for surfactant flooding

Screening optimum formulation for surfactant flooding is usually time consuming, and correctly modeling microemulsion phase behavior is critical for chemical flooding simulation. This paper extends the physics based Hydrophilic Lipophilic Difference (HLD) Net Average Curvature (NAC) model, and comprehensively demonstrated its capabilities in predicting the optimum formulation and microemulsion phase behavior. This paper uses quantitatively characterized HLD parameters, accurately predicted four optimum surfactant formulations for a target reservoir. This paper measured surfactant head area of extended surfactants and further predicted the equilibrium interfacial tension of four phase behavior test. Comparing to the empirical Hand's rule phase behavior model, the HLD-NAC equation of state shows great advantages in helping formulation design and modeling microemulsion phase behavior. Surfactant flooding sandpack laboratory tests are also interpreted by UTCHEM chemical flooding simulator coupled with the HLD-NAC phase behavior model. The results indicate the significance of HLD-NAC equation of state in not only shorten the surfactant screening processes for formulators, but also predicting microemulsion phase behavior based on surfactant structure. A compositional reservoir simulator with such an equation of state will increase its predictability and hence help with the design of surfactant formulation.