Pedagogical applications of all-atom molecular dynamics simulation in coal seam seepage mechanics

The low efficiency of water injection in low-permeability coal seams is the primary problem restricting safe production in coal mines. Self-diverting acidizing technology can effectively solve the problem of water injection in low-permeability coal seams through the uniform distribution of acid solution, and has become the core teaching content of coal seam seepage mechanics courses. However, the micro mechanism of this technology is complex and abstract, especially the gel state change of viscoelastic surfactant in the process of downhole flow, which constitutes the difficulty and pain point of the course teaching. This study innovatively introduces all-atom molecular dynamics simulation (AAMD) into teaching. By simulating and analyzing the aggregation morphology, number of hydrogen bonds, number of clusters formed under different conditions, and rotation radius of viscoelastic surfactant molecules in self-diverting acid solution under different acid concentrations and inorganic salt ion conditions, students can directly observe the changes in key microscopic parameters. Compared to traditional experimental demonstrations or theoretical deduction methods, the AAMD method can intuitively and dynamically reveal molecular scale interactions and structural evolution, transforming abstract mechanisms into visual teaching content and effectively reducing the difficulty of understanding complex mechanisms. This study provides a new method for teaching coal seam seepage mechanics.