The knowledge of the relationship between the molecular structure of surfactants and their ability to form a single phase solution for water and oil has been expanded enormously over the last two decades, primarily because the use of microemulsion solutions for EOR are promising. The qualitative trends and sensitivities between the characteristic of microemulsion solutions and the phase behavior of mixtures of oil, water and surfactants are often obtained from experiment. The experiments are simple but laborious especially when it often involves a wide range of surfactant choice. In this paper, we demonstrate a complementing molecular chemistry modeling method to assist in reducing the huge experimental test matrix in shortlisting promising surfactants for a chemical EOR design.

Application of molecular chemistry modeling for optimal microemulsion formation in chemical EOR application is a niche technology within the oil and gas industry. The modeling approach used in our simulation is based on the physical chemistry of an optimal microemulsion interface which is planar with zero surface tension and torque. The approach is implemented using the framework of Dissipative Particle Dynamics (DPD) technique. The simulation system comprises of oil, brine and surfactant in the form of coarse-grain (CG) beads. Atomistic parameters for both bonded and non-bonded CG beads are determined to simulate the molecular interactions within the system. This setup enables the computation of surface tension and torque as a function of the distance across the interface. Optimal salinity for for-mation of optimal microemulsion is determined from the profile of torque versus salinity at zero torque. The simulation results for various surfactants are compared with optimal salinity determined experimen-tally. The simulation results are in good agreement with the experimental data.

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