Miscible gas flooding has been used for enhanced oil recovery for many years. Considerable data exists for CO2 and enriched hydrocarbon flooding so that screening criteria can be applied to determine when miscible flooding with these gases could be successful. However, for nitrogen the data are much more sparse. Thus, previous screening tools are very imprecise. In fact, all four correlations for nitrogen minimum miscibility pressure available in the literature predicted miscibility pressures that were more than 1000 psi different from the measured value for more than a third of the data available in the literature.

This paper presents a new much more accurate correlation for nitrogen MMP. This correlation takes into account the effects of oil composition and reservoir temperature and matches all nitrogen MMP data in the literature within 750 psi. This correlation predicts that the nitrogen MMP of an oil decreases as the methane- or intermediate content of the oil increases, and that the nitrogen MMP increases as the mol weight of the oil increases. It also shows that the nitrogen MMP goes through a maximum as the temperature increases and that this maximum is a function of oil composition.

In addition, this paper summarizes available nitrogen MMP data and presents seven new data points.

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