Multiphase flow model of CO2 and formation fluid for production wellbores in CO2 geological storage

• Propose a flow pattern identification method for CO 2 –formation fluid systems in production wellbores via CFD simulation. • Incorporate interphase mass transfer mechanisms into wellbore pressure drop analysis for CO 2 flooding wells. • Proposed supercritical flow pressure drop method for CO 2 geological storage and production processes. • Field tests show pressure errors within ±10 %, supporting CO 2 geological storage operations. Accurate prediction of multiphase flow behavior in production wellbores is critical for understanding CO 2 migration and fluid dynamics during geological carbon storage. However, existing wellbore multiphase flow models have limited capability in accurately describing the coupled hydrodynamic and thermodynamic behavior of gas–liquid mixtures under high-CO 2 and high-pressure conditions, due to the strong non-ideal thermophysical and phase-behavior characteristics of CO 2 –formation fluid systems. This study develops an improved multiphase flow model that couples a modified flow-pattern identification approach with an interphase mass-transfer model based on flash-calculation theory. A novel method is proposed for identifying multiphase flow patterns in CO 2 flooding production wells. Additionally, leveraging the fluid phase characteristics of an oil field that is undergoing CO 2 flooding for a period of time, an interphase mass transfer model for the wellbore is developed. By integrating this model with the newly proposed flow pattern identification method, an improved predictive model for wellbore pressure drop is established. The model’s reliability is validated using actual wellbore pressure data. For example, when applied to a CO 2 flooding production well in an oilfield, the predicted pressure values closely match the measured data, with a relative average error of −1.9% and an absolute average error of 7.15%, demonstrating high accuracy. The developed model provides a robust theoretical and technical foundation for optimizing CO 2 injection and production strategies in geological storage and EOR operations.