## 1 Introduction  
The CO\({}_{2}\)-enhanced oil recovery (EOR) method has been widely applied to numerous field projects around the world [1, 2]. CO\({}_{2}\)-EOR was mostly aimed at recovering residual oil initially, but it is converted to not only increase recovery but also achieve reduction greenhouse gases by injecting CO\({}_{2}\) or flue gas. Recently, the application has been extended to unconventional hydrocarbons such as gas hydrates [3]. Existing CO\({}_{2}\)-EOR aimed to produce maximum oil and inject minimum CO\({}_{2}\), but carbon capture, utilization, and storage (CCUS) consider the increase in oil recovery and greenhouse gas storage [4, 5, 6]. With atmospheric CO\({}_{2}\) concentrations continuing to rise worldwide, CCUS has the potential to reach net-zero [7]. As a key technology used to reduce carbon dioxide emissions from fossil-fueled power plants and other industrial activities, CCUS helps provide energy security by lowering emissions while achieving economics. CCUS is considered as an important technology for moving toward a global low-carbon economy. There are many sources of CO\({}_{2}\) such as natural gas reservoirs containing CO\({}_{2}\), industrial or anthropogenic sources, and natural CO\({}_{2}\) reservoirs. Depending on the capture approaches (post-combustion, oxy-fuel, or pre-combustion), various impurities such as N\({}_{2}\), O\({}_{2}\), H\({}_{2}\)S, CH\({}_{4}\), Ar, and water are contained in the CO\({}_{2}\) stream [8, 9, 10, 11, 12]. The CO\({}_{2}\) concentration used for EOR commonly requires extremely high purity (around 90-98%), especially for miscible displacement [13]. A purification process is generally required to obtain the appropriate CO\({}_{2}\) concentration from the source gas [14]. The purity of captured CO\({}_{2}\) largely depends on the type of capture technology. The type and amount of impurities in the CO\({}_{2}\) stream affect the fluid properties and thermodynamics of CO\({}_{2}\) differently, exhibiting beneficial or negative effects on CO\({}_{2}\)-EOR: fluid solubility, phase behavior of the oil and gas system, and miscibility [15; 16]. A small number of impurities significantly changes the physical properties and phase behavior of the CO\({}_{2}\) mixtures. The solubility in water depends on the type and amount of impurities in the CO\({}_{2}\) stream [17; 18; 19]. The solubility of CO\({}_{2}\) in water increases with increasing pressure and decreasing temperature. Most impurities have low solubility in water compared with CO\({}_{2}\). Impurities reduce the partial pressure of CO\({}_{2}\) and therefore reduce solubility in water. CO\({}_{2}\) impurities can affect all stages of CO\({}_{2}\)-EOR, from CO\({}_{2}\) capture to flooding. Since the level of contaminant removal is determined by process technology and cost, the actual level of CO\({}_{2}\) purity required depends not only on the requirements of transportation and storage but also on the economics of the process. Separating impurities greatly increases the capture cost. Higher CO\({}_{2}\) purity is associated with higher costs of capture. The cost of a low purity CO\({}_{2}\) stream (82.9 wt.% CO\({}_{2}\)) is 42% lower than high purity CO\({}_{2}\) (99.98 wt.% CO\({}_{2}\)) in a capture plant [14]. It can be economical to inject the impurities contained in the CO\({}_{2}\) together. Several studies have investigated the effects of contaminants in the CO\({}_{2}\) stream on minimum miscibility pressure (MMP) to determine how impurities affect MMP compared with pure CO\({}_{2}\). In general, impurities including CH\({}_{4}\), SO\({}_{2}\), O\({}_{2}\), and N\({}_{2}\) have been found to increase MMP, while H\({}_{2}\)S, C\({}_{2}\)H\({}_{6}\), or intermediate hydrocarbons such as C\({}_{3}\) or C\({}_{4}\) reduce MMP, positively affecting miscible displacement [8; 16; 20; 21; 22]. Based on the effect of individual impurities on the phase behavior and MMP of the CO\({}_{2}\)-hydrocarbon system, the effect of impurity mixtures on MMP and EOR performance has also been examined [16].