Development of a hybrid approach to couple chemical and compositional models in an implicit, parallel simulator

by
Abraham K. John , MSE

University of Texas at Austin, 2003
Supervisors: Gary A. Pope
Kamy Sepehrnoori

Increased oil production using improved oil recovery processes requires the capability to simulate reservoir models and flow processes at high detail. The computational work required in such simulations is very large, which is a strong motivation to develop implicit algorithms and perform parallel computing. Developing and implementing fully implicit procedures for modeling both hydrocarbon and surfactant phase behavior simultaneously is a complex process. An approach to integrate the surfactant phase behavior model into an existing fully implicit, parallel, equation of state (EOS) compositional simulator is presented. The main assumptions are of dilute surfactant behavior and absence of gas in a displacement process where solubilization effects are negligible. The aqueous species transport is calculated explicitly using the results obtained from the EOS model at the end of every converged time step and the phase behavior calculated using Hand's rule. The effect of the lowered interfacial tension in presence of surfactant leads to an increase in mobilization of trapped oil. This effect is captured using a fully implicit formulation of the trapping number model for relative permeability. Test results are presented comparing the model output with the UTCHEM simulator. Results of typical chemical flood scenarios are presented both in serial and parallel mode. Time step sensitivity of the hybrid approach is compared to Implicit-Pressure, Explicit Concentrations (IMPEC) model demonstrating the use of larger time step sizes without loss of stability. This approach is an easy and efficient way of enhancing existing compositional simulators used for hydrocarbon reservoir simulation.

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