## 1 Introduction
Theoretical analyses by [PERSON] [31], [PERSON] [32], and [PERSON] [33] concluded that bubble-point pressure decreases as pore size reduces, with the effect being more pronounced under conditions further from the critical point. [PERSON] [32] coupled capillary pressure with phase equilibrium equations, solving nonlinear fugacity equations and showing that micropores reduce fluid saturation pressure. [PERSON] et al. [34] proposed a phase equilibrium calculation method that incorporates pore throat-fluid molecule interactions and capillary forces, verifying through methane, butane, and octane mixtures that pore throat diameters below 10 nm significantly impact phase behavior. [PERSON] [35] further corrected the PR-EOS for Bakken shale oil by accounting for capillary effects on two-phase systems. These improvements to the traditional PR-EOS, considering capillary pressure and nanopore confinement effects, have been applied in numerical simulations of tight oil reservoirs [36; 37; 38; 39]. However, the iterative computation required for component simulation and EOS adjustments increases computational complexity, limiting industrial adoption. As a result, these approaches are primarily used as alternatives when the accuracy of black oil simulations is insufficient. To address convergence issues caused by the strong nonlinearity in compositional simulation, many researchers have employed multiscale techniques to optimize the method. These techniques construct multiscale basis functions for coarse grids using fine-scale detailed information, enabling the upscaling and downscaling of data across scales and achieving effective multiscale coupling. The mathematical foundation of the multiscale finite element method (MsFEM) originated from the pioneering work of [PERSON] and [PERSON] [40,41]. [PERSON] and [PERSON] [40] extended this concept to elliptic equation problems, introducing the innovative MsFEM. Building on this, [PERSON] [42] proposed the multiscale finite volume method (MsFVM), inspired by MsFEM, and applied it to incompressible flow in porous media. [PERSON] and [PERSON] [43], along with [PERSON] and [PERSON] [44], further extended the approach to black oil simulations. To address the challenges posed by reservoir models with complex geological structures, [PERSON] and [PERSON] et al. [45, 46, 47] incorporated the algebraic multigrid concept, developing multiscale formulations based on operator algebraic representations. These advancements have significantly enhanced the efficiency and applicability of multiscale methods in reservoir simulations. A review of previous studies reveals that no existing multiscale compositional numerical simulation method for tight oil reservoirs incorporates the effects of capillary forces in phase behavior. Building on prior research, this study first modifies phase behavior calculations to account for capillary forces, proposing a phase calculation method that integrates these effects. Subsequently, the traditional multiscale finite volume method is enhanced to develop a multiscale compositional numerical model that considers capillary forces. Finally, the proposed model is validated, and a parameter sensitivity analysis is performed.