Abstract: Dynamic evaluation of CO₂ flooding performance still lacks a sound theoretical basis,which relies heavily on numerical simulation,and is difficult to apply in real time.To solve these problems,a novel characteristic-curve equation and a theoretical dynamic prediction chart for CO₂ flooding were established on the basis of material balance principles and mathematical derivation.The results show that the proposed prediction chart overcomes the limitations of traditional methods that rely on fitting field data and lack physical-mechanism support.It can quantitatively characterize the mathematical functional relationships among key parameters and,together with the theoretical chart,realize real-time dynamic evaluation and prediction of CO₂ flooding performance.Validation against numerical simulation results and actual production data indicates that,during the medium-to-high pseudo water-cut gas-rate stage,the prediction accuracy of the chart exceeds 90%.When the pseudo water-cut gas rate is greater than 90%,the prediction accuracy is further improved.In an application to a block of a certain oilfield,the chart predicts an ultimate recovery factor of 42%;the theoretical curve is in good agreement with the actual production performance,showing relatively high accuracy and satisfactory predictive capability.This study realizes real-time dynamic evaluation of CO₂ flooding performance and provides a new approach for development scheme optimization and recovery prediction.

Key words: CO₂ flooding, material balance principle, oil displacement prediction chart, pseudo water-cut gas rate