## 1 Introduction  
Oil field development is carried out in three stages, namely, primary, secondary, and tertiary recovery. The third stage is also known as enhanced oil recovery (EOR). CO\({}_{2}\) injection/ flood is one of the EOR methods. For years, it has been well known that the optimum CO\({}_{2}\) flood depends on the miscibility condition. The miscibility condition between CO\({}_{2}\) and reservoir crude oil determines how much oil is recovered. Identification of a miscibility condition between injected gas and crude oil is important for oil recovery in EOR. The miscibility is described as the ability of two or more substances to form a single homogeneous phase when mixed in all proportions [1]. The miscibility is also defined as a physical condition between two or more liquids that can be mixed in all proportions in the absence of an interface contact. If two liquid phases are formed after the addition of the amount of one liquid, then the liquids are considered to be immiscible [2]. Higher oil recovery from reservoir can be achieved by CO\({}_{2}\) displacement if the injection pressure is greater than a certain minimum pressure. This minimum pressure is hereafter defined as the CO\({}_{2}\) minimum miscibility pressure, abbreviated as MMP [3]. Other authors have defined the MMP as the lowest pressure at which the CO\({}_{2}\) injection fluid can develop miscibility with reservoir crude oil at reservoir temperature [4]. The common range of reservoir temperature, especially in Air Benakat formation where the sample was taken, is between 104 \({}^{\circ}\)F to 158 \({}^{\circ}\)F. The MMP determines whether the CO\({}_{2}\) gas injection is a miscible or otherwise an immiscible process. Many efforts have been tried to decrease MMP, one of them is by using co-solvent. Co-solvent is a substance that helps solvent mix with targeted substances. In CO\({}_{2}\) EOR, co-solvent helps CO\({}_{2}\) extract crude oil. Co-solvents, especially polar ones such as water, methanol, acetone, ethyl acetate, toluene, petroleum ether, and ethanol, are used as a modifier in CO\({}_{2}\) extraction performance [5; 6; 7; 8]. A co-solvent interacts either with the solute, solvent, or both [5]. Pressure and temperature factors affect interaction and chemical equilibria. Polarity happens when there are electronegativity differences in molecule. According to polarity, there are two types of molecules, i.e., polar and non-polar molecules. A polar molecule has net dipole, and therefore its bonds are asymmetrically arranged. Meanwhile, a non-polar molecule has zero dipole, and thus its bonds are symmetrically arranged [9]. Polarity of a molecule has an effect on its physical properties such as solubility, boiling point, and intermolecular forces [10]. Intermolecular forces, which mean attractive forces between molecules, are divided into six types which are in order from the strongest, hydrogen bond, dipole-dipole, ion-induced dipole, induced-dipole, and London dispersion [10]. Furthermore, volatility of compound and physical properties (molecular weight, boiling point, and molecular shape) are other factors that affect the solubility of CO\({}_{2}\) in crude oil [5]. From research done by [PERSON] et al. [5], [PERSON] et al. [7], and [PERSON] and [PERSON] [11], their results indicated that the solubility of CO\({}_{2}\) in acetone was larger than that in ethanol [7]. The addition of a carbonyl-group component, such as acetone, enables greater extraction of heavier compounds and higher-boiling fractions than that being extracted with the presence of a hydroxyl-group component such as ethanol [5]. This occurs because ethanol behaves as a polar and self-associated substance. Therefore, with the hydrogen bond owned by ethanol, the cohesion forces of the molecule are very strong. They also tend to interact with polar fractions and higher-boiling fractions that possibly form hydrogen bonds instead of CO\({}_{2}\). In contrast, acetone is a non-associated-polar substance because acetone does not have hydrogen bond.