Comparative Study on Numerical Simulation of CH₄ Breakthrough Pressure in Unsaturated Rock Based on Step‐By‐Step Method and Continuous Injection Method

ABSTRACT Gas breakthrough pressure is a key parameter affecting gas production and evaluation of tight reservoir sealing capabilities. This study aims to explore the impact of different injection methods on CH 4 breakthrough pressure in unsaturated rocks. COMSOL Multiphysics was used to simulate the CH 4 breakthrough process, and comparative analysis was conducted using step‐by‐step and continuous injection methods. The results show that the step‐by‐step method has higher measurement accuracy under low CH 4 breakthrough pressure and is suitable for scenarios that require precise evaluation, whereas the continuous injection method is more efficient under high CH 4 breakthrough pressure and is suitable for rapid evaluation needs. According to outcomes of simulation, this research suggested a numerical optimization framework aimed at forecasting the breakthrough pressure of CH 4 and verified the accuracy and applicability of the model through linear fitting of experimental data and predicted values. In addition, the study also conducted a sensitivity analysis on the pore distribution index ( m ) and injection flow rate ( u in ) in the van Genuchten model. The results show that u in has a small impact on breakthrough pressure, whereas m has a considerable effect on breakthrough pressure. An increase in m leads to an increase in breakthrough pressure, thereby enhancing the sealing performance of rock core. This study reveals the applicability difference between the step‐by‐step method and the continuous injection method in predicting CH 4 breakthrough pressure and proposes an effective prediction method based on numerical simulation, which provides valuable insights for selecting gas injection methods and predicting breakthrough pressure in rocks. © 2025 Society of Chemical Industry and John Wiley & Sons, Ltd.