Robust Three-Phase Vapor–Liquid–Asphaltene Equilibrium Calculation Algorithm for Isothermal CO2 Flooding Applications

• Published in: Industrial & engineering chemistry research Vol. 58; no. 34; pp. 15666 - 15680
• Main Authors: Li, Ruixue, Li, Huazhou
• Format: Journal Article
• Language: English
• Published: American Chemical Society 28.08.2019
• Subjects: algorithms; asphaltenes; carbon dioxide; oil fields; oils; process design
• ISSN: 0888-5885; 1520-5045; 1520-5045
• DOI: 10.1021/acs.iecr.9b02740

CO2 flooding is an effective enhanced oil recovery process for light oil reservoirs. Asphaltenes can easily precipitate during CO2 flooding, leading to the appearance of three-phase vapor–liquid–asphaltene (VLS) equilibria. A prerequisite for accurately simulating the CO2 flooding process is developing a robust three-phase VLS equilibrium calculation algorithm. In this study, we develop a robust and efficient three-phase VLS equilibrium calculation algorithm with the use of asphaltene precipitation model proposed by Nghiem et al. [Efficient Modelling of Asphaltene Precipitation, SPE, 1993 ]. To develop this algorithm, a two-phase flash calculation algorithm is first developed to split the mixture into an asphaltene phase and a nonasphaltene phase. Moreover, two different three-phase VLS flash calculation algorithms are developed and incorporated into our three-phase equilibrium calculation algorithm. New initialization approaches for both stability test and flash calculations are proposed. The performance of this three-phase VLS equilibrium calculation algorithm is tested by generating pressure–composition (P–X) diagrams for several reservoir fluids mixed with pure or impure CO2.