Empirical Correlation of Pressure Interval of Near-Miscible Flooding for Pure and Impure CO2 Streams

It is believed that the boundaries of near-miscible pressure region are in the vicinity and closely related to minimum miscible pressure (MMP). In this paper, over 140 data sets belonging to experimental MMP values along with enough corresponding gas/oil compositional information from the literature were collected to construct a new correlation for both pure and impure CO₂. Parameters such as reservoir temperature, molecular weight of C₇⁺, solution gas and injection gas contents, are selected as the key input values. It is found that the proposed models of MMP significantly outperform the existing 10 commonly used methods and provide the best reproduction of MMP data. According to the data of previous study, the lower and upper boundaries for the pressure interval is determined as 0.87 MMP and 1.07 MMP, respectively. Thus, a new empirical correlation for the prediction of near-miscible pressure region was proposed for the first time. It should be noted that the upper boundary of the pressure interval is higher than the conventional MMP due to the inappropriateness of the determination criterion. Results showed that the newly proposed model can simulate the pressure interval based on the correlations of linear fittings and non-linear fittings for both pure and impure CO₂, respectively.