(2fw) Predictive Modeling of Phase Behavior of Reservoir Fluids Under Miscible Gas Injection Using Peng-Robinson Equation of State

Improved correlations for critical temperature, critical pressure, and acentric factor are developed for an extensive database of hydrocarbons. The correlations rely on measurements of molecular weight and refractive index at ambient conditions and utilize the concept of Aromatic Ring Index (ARI) recently developed by Abutaqiya et al. as a distinctive characterization factor for non-polar hydrocarbons (Abutaqiya et al., Energy & Fuels, 2021, 35 (2), 1113–1119). The new correlations are then implemented for modeling the phase behavior of a variety of oils under miscible gas injection in a fully predictive manner using Peng-Robinson equation of state (PR EOS). The results indicate that the proposed modeling framework yield accurate predictions for bubble pressure of oil/gas blends with an average absolute deviation of 6.4% for a wide variety of oils and injection gases including: lean, rich, H₂S, CO₂, and N₂. Additionally, an interesting cross-over behavior in the phase envelope of live oils under CO₂ injection is observed using PR EOS. This behavior has been reported in the literature for modeling results using PC-SAFT EOS and seems to be characteristic of CO₂.