An improved viscosity model for CO2-crude system

Abstract

The existing viscosity models, including LBC (Lohrenz-Bray-Clark) Model, CS (Pedersen) Model and PR (based on PR Equation of State) Model, could not take into account accuracy, theory strictness and calculation convenience simultaneously. This study considers temperatures, pressures and interaction between components and other affecting factors to improve the viscosity model based on PR EOS (equation of state) and finally establishes a new calculation model for CO2-crude system under high pressures and high temperatures. The accuracy of the PR model is improved by changing the dimensionless constant in the model into a function related to the system temperatures. Furthermore, the mixing-rule in viscosity calculation of mixture is modified through introducing the binary interac tion factor and effective mole fraction of CO2. Based on gas and liquid phase components of field oil samples from actual measurement, the calculation accuracy of models before and after improvement are compared, which shows that the new viscosity model is not only simple in computation, but also much more accurate, and finally meets the industrial requirements. Key words: CO2-crude system, viscosity model, PR EOS, viscosity mixing-rule