Multiscale analysis of solid-liquid two-phase fusion fissure plugging material (SLTP-FP) for underground coalbed methane (CBM) extraction: Plugging performance validation and microscopic molecular simulation

Underground drilling remains the predominant method for coalbed methane (CBM) extraction. Nevertheless, factors including drilling disturbances, coal rock properties, and geostresses contribute to the formation of fractures within the coal matrix, substantially limiting extraction efficiency. Traditional solid-phase plugging materials often experience shrinkage and cracking due to prolonged water loss. To address these challenges, this study introduces the solid-liquid two-phase fusion plugging material (SLTP-FP), a liquid-phase-based material designed for extended water retention. Through non-destructive scans of grouted coal samples, the study conducted both qualitative and quantitative analyses of fracture morphology and plugging efficacy. Additionally, simulation experiments were utilized to investigate the long-term water retention mechanisms of SLTP-FP. Results indicate that post-grouting, the total porosity of the coal sample dramatically reduced from 8.54% to 0.29%, attaining a plugging efficiency of 96.61%. Notably, approximately 97.24% of marked pore equivalent diameters ranged between 0 and 0.8 mm, demonstrating the material's exceptional plugging capability for microfractures. Simulations further reveal that SLTP-FP components possess high adsorption energies with water molecules, ensuring sustained water retention, with modified bentonite identified as the critical water-retaining element. In practical engineering scenarios, adjusting the quantity of modified bentonite allows adaptation to various geological conditions, thereby facilitating durable and effective plugging of CBM extraction paths.