Phase Behavior Analysis For Oil-Gas Multiphase Flow System

With the expansion of deep-sea oil and gas exploitation,demands on pipeline flow assurance including online and offline multiphase flow simulation,hydrate and wax precipitation analysis are increasing rapidly.Phase behavior analysis,as the foundation of those,is therefore facing wider application.In this thesis,study on phase equilibrium flash calculation,thermodynamic models and fluid characterization analysis was proceeded to meet the demands of oil-gas multiphase pipeline simulation and flow assurance analysis.A phase behavior calculation software named GetPVT was developed based on the study.Theoretically,essential study on flash algorithm and thermodynamic models was first performed,and further research was then proceeded based on it.Insufficiency of phase determination in classical flash algorithm was analysis,an optional flash method was therefore applied;research and application of PC-SAFT was done to better deal with heavy and polar components,an algorithm to avoid inconvergence in solving this EOS was proposed;with intensive discussion on petroleum fluid component discontinuity,two novel component characterization models were developed specifically for gas chromatography analysis,the proposed models showed about 30% less absolute average relevant error compared with other characterization method.The phase behavior analysis software GetPVT was developed based on theoretical research and previous work in the research group.This software was designed to provide fluid properties for oil-gas multiphase simulator and low-temperature high-pressure flow assurance analysis software.Functions of this software included fundamental flash calculation and property generation,fluid phase behavior analysis,property generation for multiphase flow simulation.This software also serves as modeling and testing platform for hydrate formation and wax deposition study.