Abstract: To address the dual challenges of gas accumulation-induced safety risks and carbon emission reduction in coal mine goafs, this study investigates a typical goaf in the Guqiao coal mine of the Huainan mining area as an example. A multi-physics coupled numerical simulation is conducted on gas migration and CO₂ sequestration in the goaf based on its geological structures, mining techniques, and reservoir characteristics. Using COMSOL Multiphysics, we establish a three-dimensional porous model incorporating a U-shaped ventilation system and an injection–monitoring well network. The model uses coupled equations to describe fluid flow, diffusion, adsorption, and the pressure field, and systematically analyze the porous zone, gas distribution, and key controls on CO₂ sequestration efficiency in the goaf. Simulation results indicate that the porous zone in the goaf exhibits an O-shaped ring distribution, with gases displaying vertical stratification: CH₄ accumulates at the bottom under gravity, while O₂ concentration decreases with increasing depth. Based on O₂ concentration, the goaf can be divided into several zones with different safety levels: the heat dissipation zone (0–133 m), the oxidation heating zone (128–167 m), and the suffocation zone (70–216 m). This provides a quantitative basis for defining safety constraints in the CO₂ sequestration process. Well network parameters significantly influence CO₂ migration and sequestration performance. Vertical injection at 60 m depth (within the fracture zone) yields optimal sequestration, which is 1.09 and 1.15 times higher than those at 80 and 95 m, respectively; a symmetrical four-well monitoring network achieves total CO₂ sequestration 2.21 times that of a single-well scheme, improving the uniformity of gas diffusion and reducing CO₂ leakage risk. This study reveals the coupled mechanism of the porous zone–gas migration–CO₂ sequestration in the goaf and identifies the optimal well deployment scheme. It provides a scientific basis and engineering guidance for safety management in production, goaf resource reutilization, and carbon neutrality in Huainan mining area and other coal mines with similar conditions.