The slim tube test has become a standard method to measure the MMP in the petroleum industry. The second objective is to compare this model with the other eleven most popular and relatively high-accuracy CO 2-oil MMP correlations presented in the previous literature by using other nine groups of CO 2-oil MMP experimental data, which have not been used to develop the new correlation. The first objective is to utilize the modified conjugate gradient and global optimization algorithm for establishing a four-parameter and improved MMP prediction model of CO 2-oil system, which has a wider range of application, taking advantage of 210 groups of CO 2-oil MMP experimental data tested by slim tube experiment in the literature. Most the MMP empirical correlations are proposed based on the experimental data of CO 2-oil system, while these MMP empirical correlations of CO 2-oil system have certain constraints. Thus, empirical correlation is usually used for predicting the MMP.
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Equation of state is precise and fast, but the miscibility function is difficult to give a clear judgment standard, because a characterization procedure of the plus-fraction must be used and such a characterization can have a huge influence on the calculated value. The experimental method is the standard method, but it needs to consume large amounts of time and money. The slim tube test is one of the most commonly used test methods in addition, there are rising-bubble apparatus (RBA) method, steam density method, multiple contact method, and interfacial tension vanish method. At present, prediction of the MMP commonly contains three methods: experiment, empirical correlation, and equation of state.
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The minimum miscibility pressure (MMP) at which the crude oil and CO 2 become miscible is a key factor because, in general, the CO 2 is not miscible at first contact with reservoir oils but may achieve dynamic miscibility through multiple contact. Generally, the oil recovery of miscible flooding is higher than nonmiscible flooding. IntroductionĬO 2 injection is one of the most effective methods to enhance oil recovery.
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Compared to the eleven most popular and relatively high-accuracy CO 2-oil system MMP correlations in the previous literature by other nine groups of CO 2-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 CO 2-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. 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, C 7+ molecular weight of crude oil, and mole fractions of volatile components (CH 4 and N 2) and intermediate components (CO 2, H 2S, and C 2~C 6) of crude oil. On the basis of 210 groups of CO 2-crude oil system minimum miscibility pressure data, an improved CO 2-crude oil system minimum miscibility pressure correlation was built by modified conjugate gradient method and global optimizing method.
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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.