Partition-Coefficient Relations for Improved Equation-of-State Description of Microemulsion-Phase Behavior

Victor A. Torrealba, Russell T. Johns

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Surfactant-mediated enhanced-oil-recovery (EOR) techniques, such as surfactant/polymer (SP) flooding, have received increased attention because of their ability to reduce capillary forces at the pore-scale to ultralow values and mobilize trapped oil. Recently, there have been increased efforts in microemulsion-phase-behavior modeling capabilities by relying on the hydrophilic/lipophilic-difference (HLD) measure for surfactant-affinity quantification. One common assumption of most microemulsion-phase-behavior models is the assumption of pure excess phases, which states that the surfactant component is only present in the microemulsion phase. This assumption can lead to significant errors for some surfactant systems, especially when applied to chemical simulations in which discontinuities may arise. The main novelty of this paper is to allow for surfactant partitioning into both the water and oil excess phases by use of a simple approach, and then relate relevant surfactant-partitioning coefficients (i.e., K-values) to HLD. Surfactant screening that is based on surfactant-structure parameters is also considered based on estimated K-values. Key dimensionless groups are identified as a function of activity coefficients, which allow for a simplified description of the surfactant-partition coefficients. These surfactant-partition coefficients are combined with the chemical-potentials (CP) equation-of-state (EoS) model to describe and predict the phase behavior when the excess phases are not pure. Further, the developed surfactant-partitioning model can be used in other microemulsion-phase-behavior models to allow for impure excess phases.
Original languageEnglish (US)
Pages (from-to)1899-1908
Number of pages10
JournalSPE Journal
Issue number05
StatePublished - Oct 17 2018

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank the member companies of the Enhanced Oil Recovery JIP in the EMS Energy Institute at Pennsylvania State University at University Park, Pennsylvania, for their financial support. Russel T. Johns is chair of the undergraduate Petroleum and Natural Gas Engineering Program, and holds the Victor and Anna Mae Beghini Faculty Fellowship in Petroleum and Natural Gas Engineering at Pennsylvania State University. He also holds the Energi Simulation Chair in Fluid Behavior and Rock Interactions at Pennsylvania State University.


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