An Experimental and Modeling Framework for High-Pressure, High-Temperature Microemulsion Optimum FormulationYoga, Hanif microemulsion phase behaviormicroemulsion optimum formulationhigh-pressure experimentsurfactant floodingchemical enhanced oil recoveryEnergy and Mineral EngineeringPHDSurfactant enhanced oil recovery (EOR) requires an optimum formulation condition at which oil and water are solubilized equally in a microemulsion phase and ultralow interfacial tension is attained. This dissertation addresses two challenges in predicting this condition under reservoir-relevant conditions: reliable characterization of crude-oil hydrophobicity through equivalent alkane carbon number (EACN), particularly for live oils, and accurate description of pressure effects and pressure-oil composition interactions on microemulsion optimum formulation. A consistent EACN determination framework is developed using salinity scan data, inverse solubilization analysis, and the HLD-NAC equation-of-state framework. The results show that objective determination of optimum salinity provides consistent EACN estimates for dead and live crude oils, that nonlinear oil mixing rules are not required for the literature data considered, and that pressure corrections are important for live-oil EACN determination. High-pressure, high-temperature surfactant-oil-water experiments were also conducted using alkanes of different carbon numbers to evaluate the effect of pressure on optimum temperature. The results show that pressure-induced phase-volume changes and interphase mass transfer depend strongly on oil composition: lighter oils promote oil transfer into the microemulsion phase, whereas heavier oils show reduced oil transfer and increased water transfer. Optimum temperature measurements demonstrate that pressure and oil composition are interdependent formulation variables, leading to an inversion in pressure effects across different oils. To capture this behavior, an optimum formulation model with explicit pressure-ACN interaction terms was developed. Overall, this dissertation improves the prediction of microemulsion optimum formulation by providing a reliable framework for crude-oil EACN determination and demonstrating the importance of pressure-oil composition interactions for surfactant EOR design under reservoir conditions.Ali Borhan, Outside Unit & Field MemberLuis Ayala H, Major Field MemberAnne Menefee, Major Field MemberHamid Emami-Meybodi, Chair & Dissertation AdvisorShimin Liu, Program Head/ChairRussell T Johns, Special Signatoryopen_access2026-07-10T21:06:22Zhttps://etda.libraries.psu.edu/catalog/28952hfy5084