## 3 Results and Discussion
### Sensitivity Analysis
#### 3.2.2 Key Findings on the Impact of Capillary Forces on Tight Oil Production  
This section uses fluid data from [PERSON]. [PERSON] et al. [60], including mixture composition, basic properties, and binary interaction parameters. A simple closed-external-boundary cubic reservoir model, incorporating 5 vertical wells and a hydraulic fracture (as detailed in Table 3), was created with 5000 grid cells. The grid size settings are based on [PERSON]'s research [49]. As shown in Figure 9, the five vertical wells form a five-spot pattern, with four injection wells at the reservoir edges and one production well at the center. A black line indicates the hydraulic fracture, and the target grid is marked with a red star. The production well operates at a constant pressure of 10 MPa, while the injection wells inject CO\({}_{2}\) at a constant rate of 300 m\({}^{3}\)/day. The injection and production period lasts 10 years. The relative permeability curves used in the simulation refer to the core displacement test report of a certain block in the Changing Oilfield, China. The specific data can be found in Figure 10.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Component** & **Pc (Bar)** & **Tc (K)** & **Vc (L/mol)** & **Mol. Weight** & **Accentric Fact** & \begin{tabular}{c} **Initial Total** \\ **Composition Values** \\ \end{tabular}  \\ \hline N\({}_{2}\)/CH\({}_{4}\) & 45.8 & 189.5 & 0.0997 & 16.1594 & 0.01142 & 0.463 \\ CO\({  
This section presents four scenarios:  
Base Case: In gas-phase equilibrium calculations, existing numerical simulators neglect the impact of confinement on fluid phase behavior in nanopores. Consequently, capillary pressure effects and shifts in critical properties are excluded. Case 1: Capillary forces are calculated using the Young-Laplace equation with a pore radius of 20 nm. Case 2: Capillary forces are calculated using the Young-Laplace equation with a pore radius of 35 nm. Case 3: Capillary forces are calculated using the Young-Laplace equation with a pore radius of 50 nm. The proposed multiscale compositional simulator is used to analyze the influence of capillary forces on cumulative production, component distribution, and reservoir saturation. Based on the results of the four scenarios, the impact of capillary forces on cumulative production was analyzed. As shown in Figure 11, including capillary forces (Case 1-3) generally leads to higher cumulative oil production compared to the scenario without capillary effects (Base Case). The smaller the pore radius, the more pronounced the capillary effect, resulting in a greater increase in cumulative oil production. This underscores the importance of considering capillary forces in tight oil reservoir development. It is important to note that this section primarily addresses how capillary pressure influences phase behavior and, consequently, oil recovery efficiency. However, in the actual development of tight oil reservoirs, various complex mechanisms and operating conditions must be considered. For instance, capillary trapping effects play a role during multiphase flow in tight oil reservoirs. Therefore, capillary pressure should not be viewed as the sole key mechanism for improving oil recovery. Figure 11: Comparison of cumulative oil production across different scenarios. Figure 10: Relative permeability curves (The data comes from a core displacement test in the Changing Oilfield). Figure 12 shows that capillary forces (Case 1-3) inhibit the increase in gas-phase components. This is due to a decrease in the bubble point and dew point lines caused by capillary effects. Smaller pore radii result in a more significant decrease, which leads to an increase in the liquid phase and a relative reduction in the gas phase. The impact of capillary forces on component distribution was analyzed, focusing on the cell marked by a red star in Figure 9. The molar fractions of components in this cell under the Base Case and Case 1 were compared.