A variety of correlations for the estimation of CO2 Minimum Miscibility Pressure (MMP) have been proposed. Although some of them are less accurate, the correlations are helpful in roughly screening a candidate reservoir for CO2 flooding and in designing CO2 parameters without detailed characterizations. However, the existence of nanoscale pores in tight oil reservoirs affects fluid phase equilibrium, resulting in a lower CO2 MMP. The correlations must be revised to predict MMP for CO2 injection in tight oil reservoirs.

This paper summarizes most CO2 MMP correlations. A CO2 MMP analysis is processed by CMG Winprop to validate each correlation for tight oil samples including Cardium, Bakken, Montney, Eagle Ford and Niobrara reservoirs. Afterwards, an integrated correlation for CO2 MMP is proposed with the consideration of nanoscale pore confinement.

In general, a correlation with molecular weights and reservoir temperature can give an estimation of CO2 MMP. Furthermore, for tight oil reservoirs, taking the confinement effect into consideration, CO2 MMP is reduced and a solubility method can incorporate a pore radius into evaluation.

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