Optimized critical parameters for n-alkanes up to C100 for reliable multiphase behavior of hydrocarbon mixture using SRK EOS

Abstract

The Soave-Redlich-Kwong equation of state (SRK EOS) is widely used for phase behavior simulation of hydrocarbon mixtures. However, its applicability and reliability are limited for heavier hydrocarbon mixtures and reservoir fluids. This research presents optimized critical temperatures (TC), critical pressures (PC), and acentric factors (ω) parameters for n-alkanes up to C100 for improved volumetric and compositional multiphase behavior predictions.Parameters TC, PC, and ω for C7 to C100 are optimized using Particle Swarm Optimization (PSO) to match the density as well as vapor pressure data. Average absolute relative deviations (AARDs) achieved are 1.9% and 2.4% respectively for density and vapor pressure matches, corresponding values for the unoptimized case are 53.23%, and 3.90% respectively. The case of optimization of ω only to match vapor pressure has AARD of 2.0% in comparison to 3.90% from unoptimized values.Binary interaction parameters (BIPs) are optimized by matching upper critical end point (UCEP) for CO2, CH4, C2, and C3 binaries with n-alkanes with their optimized TC PC ω, optimized ω (and unoptimized TC and PC) only, and unoptimized TC PC ω values cases. It is found that optimized TC PC ω is correctly able to show the presence of three-phases for all 23 ternary hydrocarbon mixtures.