Abstract
A simple and novel approach is proposed to represent the mutual solubility of water and hydrocarbon components based on equations of state at high temperatures in thermal recovery processes. Sϕreide and Whitson modifications are applied to the Peng–Robinson (PR) equation of state (EOS) so that all components, including the water component, can exist in all phases, reasonably representing gas solubility in water and water solubility in hydrocarbon phases. We propose an algorithm to assign binary interaction parameters (BIPs) for aqueous and nonaqueous phases. The water vapor pressure helps select initial K-values for stability analysis so that the aqueous phase can be split out first if present. The algorithm is tested by a wide range of variations in pressure, temperature, and composition. The results show the robustness of the algorithm and the effects of temperature and overall water mole fraction on phase behaviors in steam flooding processes.
Highlights
Water is present either as initial water or as injection water and in contact with hydrocarbon phases in equilibrium in reservoirs
To quantify the mutual solubility of water and hydrocarbons, we examine water solubility in the oleic phase and hydrocarbon solubility in the aqueous phase at different temperatures in the three-phase region
This example uses a synthetic oil mixture taken from Luo and Barrufet,52 which consists of 0.25 water, 0.15 pseudocomponent 1 (PC1), 0.15 pseudocomponent 2 (PC2), 0.2 pseudocomponent 3 (PC3), and 0.25 pseudocomponent 4 (PC4)
Summary
Water is present either as initial water or as injection water and in contact with hydrocarbon phases in equilibrium in reservoirs. Whitson and Brule verify the accuracy of simultaneous application of aqueous- and nonaqueous-phase interaction coefficients for mutual-solubility predictions of binaries and natural gas/water/brine mixtures, suggesting that the modification is warranted. We present the binary interaction parameter correlations from Sφreide and Whitson and the α function for water from Li and Yang, followed by the characteristic of the water vapor pressure curve. According to Sφreide and Whitson, two sets of binary interaction parameters (BIPs) between hydrocarbon components and water are proposed for nonaqueous phases and the aqueous phase. Two different attraction terms in the EOS are calculated as a function of their respective BIPs. Sφreide and Whitson suggested that a constant BIP for the nonaqueous phase and a temperature-dependent BIP for the aqueous phase were found adequate to match experimental mutual solubility data with reasonable accuracy.
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