Abstract
Minimum miscibility pressure (MMP), which plays an important role in miscible flooding, is a key parameter in determining whether crude oil and gas are completely miscible. On the basis of 210 groups of CO2-crude oil system minimum miscibility pressure data, an improved CO2-crude oil system minimum miscibility pressure correlation was built by modified conjugate gradient method and global optimizing method. The new correlation is a uniform empirical correlation to calculate the MMP for both thin oil and heavy oil and is expressed as a function of reservoir temperature, C7+molecular weight of crude oil, and mole fractions of volatile components (CH4and N2) and intermediate components (CO2, H2S, and C2~C6) of crude oil. Compared to the eleven most popular and relatively high-accuracy CO2-oil system MMP correlations in the previous literature by other nine groups of CO2-oil MMP experimental data, which have not been used to develop the new correlation, it is found that the new empirical correlation provides the best reproduction of the nine groups of CO2-oil MMP experimental data with a percentage average absolute relative error (%AARE) of 8% and a percentage maximum absolute relative error (%MARE) of 21%, respectively.
Highlights
CO2 injection is one of the most effective methods to enhance oil recovery [1]
The oil recovery of miscible flooding is higher than nonmiscible flooding
Empirical correlation is usually used for predicting the minimum miscibility pressure (MMP)
Summary
CO2 injection is one of the most effective methods to enhance oil recovery [1]. Generally, the oil recovery of miscible flooding is higher than nonmiscible flooding. Prediction of the MMP commonly contains three methods: experiment [3], empirical correlation [4], and equation of state [5, 6]. Most the MMP empirical correlations are proposed based on the experimental data of CO2-oil system, while these MMP empirical correlations of CO2-oil system have certain constraints. MMP prediction model of CO2-oil system, which has a wider range of application, taking advantage of 210 groups of CO2oil MMP experimental data tested by slim tube experiment in the literature. The second objective is to compare this model with the other eleven most popular and relatively highaccuracy CO2-oil MMP correlations presented in the previous literature by using other nine groups of CO2-oil MMP experimental data, which have not been used to develop the new correlation. (1) Pure CO2 (2) Reservoir oil (3) Valve (4) Slim tube (5) Constant temperature air bath (6) Back-pressure valve (7) Separator (8) Gasometer (9) Nitrogen (10) Automatic pump
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