Application of a compositional calculator and adaptation of PVT calculations to real field data with abnormal fluid properties

UDK: 622.276, 620.193

DOI: 10.24887/0028-2448-2025-9-42-48

Key words: PVT modeling, compositional modeling, phase equilibria, equation of state (EOS), dew-point pressure, empirical correlations

Authors: V.L. Malyshev (Ufa State Petroleum Technological University, RF, Ufa); A.L. Remizov (Ufa State Petroleum Technological University, RF, Ufa); E.S. Ivanaevskaya (Ufa State Petroleum Technological University, RF, Ufa); E.F. Moiseeva (Ufa State Petroleum Technological University, RF, Ufa); K.R. Churakaev (Ufa State Petroleum Technological University, RF, Ufa); E.V. Yudin (Gazprom Neft Companу Group, RF, Saint Petersburg); M.I. Gudilov (NEDRA LLC, RF, Saint Petersburg); S.V. Zamakhov (NEDRA LLC, RF, Saint Petersburg)

Development of digital twins to describe multiphase flows in wells, gathering systems, and wellstream processing requires precise mathematical models capable of simulating phase transitions in multicomponent mixtures. Currently, Western software products dominate the market for PVT modeling of hydrocarbon mixtures. However, their commercial licensing, proprietary (closed-source) nature, and lack of adaptability to industry-specific needs limit their applicability. Consequently, the development of domestic software for modeling reservoir fluid phase behavior is a critical priority for the oil and gas industry. This paper presents the results of compositional modeling of multiphase hydrocarbon systems with abnormal properties due to their unique composition, using a proprietary PVT calculator. The authors detail the implementation of a software algorithm for calculating hydrocarbon phase behavior under specified pressure-temperature (PT) conditions based on a cubic equation of state (EOS). The simulation results are compared with those from established commercial software and laboratory experimental data. Simplified approaches to compositional modeling of gas-condensate mixtures are analyzed, particularly those relying on empirical correlations. A comparative study of various computational methods for determining the dew-point pressure of gas-condensate mixtures is conducted using field examples of a field in Russia. The study demonstrates that empirical correlations have significant limitations in applicability across broad pressure and temperature ranges, whereas classical equations of state accurately describe fluid phase behavior under dynamic PT conditions corresponding to all stages of production.

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