Equation of State Based Thermal Compositional Reservoir Simulator for Hybrid Solvent/Thermal Processes
Date
2014-04-28
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Abstract
In the earlier generations of thermal compositional simulators, several assumptions are used for representing the characteristics of dead oil and steam mixtures. The K-Value approach is used for phase splitting and equilibrium ratios are considered to be functions of only temperature and pressure. Phase properties such as density, enthalpy and internal energy are calculated from correlations using ideal solution assumption. Excess properties such as excess enthalpy and density and mutual solubility of water in oil phase and vice versa are neglected in such models.
These assumptions may work well for simple fluid mixtures with pure steam injection but could produce false results in more complicated processes such as the hybrid processes involving injection of hydrocarbons with steam. In such processes, where a hydrocarbon is added to the steam, equilibrium ratios change with the variation of composition, and neglecting this effect may lead to thermodynamically inconsistent or wrong results. Solubility of water in oil phase increases with temperature and it could become significantly high in some cases.
In this study, a new 3-D, fully implicit, equation of state (EOS) based thermal compositional simulator capable of modeling hybrid and thermal processes of heavy oil recovery was developed. By using an equation of state, our goal is to correctly model the thermodynamic and compositional effects on the phase behavior. Water is allowed to be soluble in all phases and mutual solubility of oil and water is taken into account in this simulator and its effect on the oil recovery can be investigated. Thermal expansion, fluid compressibility, solvent extraction, and steam distillation are calculated by an EOS based thermodynamic model. Steam properties are calculated from EOS or steam tables.
A new isenthalpic multiphase flash calculation was also developed and was integrated in the thermal compositional simulator. The flash calculation method uses a modified Rachford-Rice monotonic objective function and the negative flash concept for phase distribution and phase identification. Therefore phase stability analysis is not necessary and the flash method is not computationally expensive. The new isenthalpic multiphase flash calculation shows no difficulty in handling difficult situations such as narrow boiling point regions and appearance and disappearance of different phases which is common in thermal processes.
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Engineering--Petroleum
Citation
Heidari, M. (2014). Equation of State Based Thermal Compositional Reservoir Simulator for Hybrid Solvent/Thermal Processes (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25929