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CO2 flooding has been successfully proven to increase oil production. One of the most critical parameters for designing a CO2 flooding project is determining the Minimum Miscibility Pressure (MMP) value. Therefore, an accurate determination of the MMP is required for the CO2 flooding project. Several researchers have developed methods for determining MMP measurement techniques. Examples include the slim tube test and core flood, rising bubble apparatus (RBA), pressure/composition (P/X) diagram, oil swelling/extraction test, and, more recently, vanishing interfacial tension (VIT). However, the current method of determining MMP leaves the remaining questions. It is then necessary to comprehensively investigate the phase behavior and the effect of interactions between CO2 and crude oil systems to determine the criteria and factors for determining MMP. Many studies have investigated the fundamentals of the CO2 flow mechanism and its interactions with hydrocarbon fluid on oil volume swelling, vaporization/extraction phenomena, and IFT reduction. However, little research has been conducted to investigate the mechanisms of CO2 and hydrocarbon fluid interactions on crude oil stability and its impact on oil recovery performance. Therefore, this research aims to investigate the critical factors affecting the mutual interactions between CO2 and crude oil through their phase behavior and observe the effect of CO2 flooding on crude oil stability and recovery performance in porous media. The steps of this study are divided into three parts: preliminary experiments, main experiments, and analyses of the composition of crude oil residue. Preliminary experiments consist of SARA analyses, compositional analyses, and solid detection. The main experiments include swelling, extraction observation, and slim tube experiments. Lastly, analyses of the composition of crude oil residue were conducted to investigate crude oil stability. The experiments were conducted on two different crude oil samples, RDG and JTB, at a reservoir temperature of 90oC, and re-conducted at a temperature of 70oC, approximately the average temperature of the surface and reservoir field, to investigate the effect of temperatures on the swelling and extraction phenomena and the CO2 displacement performance. The experimental results showed that the pressure at which the oil started shrinking significantly depends strongly on the temperature and composition of the oil. It was also found that the extraction of hydrocarbons from crude oil usually increases with gas density (CO2) and pressure. Lower temperatures usually lead to a higher CO2 density, thereby causing a rapid increase in the extraction with pressure. Therefore, the MMP estimation through the swelling and extraction method was found to be uncertain due to asphaltene. This study has shown that changes in pressures, temperatures, and oil composition due to CO2 flooding significantly impact crude oil stability. This affects oil recovery performance and MMP measurement using the CO2 displacement process. Crude oil stability also strongly depends on all the crude oil composition (saturates, aromatics, resins, and asphaltenes) behavior and the percentage of each component.