Impact of fines migration and clogging on gas production in hydrate-bearing sediments: A 2D microfluidic pore model and 3D DEM-CFD study

Natural gas hydrate, as a promising unconventional energy source, often experiences the migration and accumulation of fine particles during the gas extraction process, leading to pore clogging and permeability decline. These effects reduce gas production efficiency and compromise reservoir stability. However, a systematic understanding of the microscopic mechanisms governing fine particles migration remains lacking. This study investigates the influence of fine type, pore-throat size, pore fluid chemistry, as well as hydrate saturation, and depressurization conditions on fines migration, clogging, and permeability evolution using both two-dimensional microfluidic pore model experiments and three-dimensional DEM-CFD coupled numerical simulations. The experimental results demonstrate that the electrical sensitivity of fines and pore-throat geometry jointly determine the critical pore-clogging concentration. Cohesive representative fines—montmorillonite—tends to form flocculation structures in saltwater, while non-cohesive fines—silica particles—exhibit high mobility. Numerical simulations further reveal that a higher depressurization gradient and lower saturation increase the fines migration rate and permeability while slowing the clogging evolution process during hydrate dissociation. The findings indicate that fines migration behavior has strong multi-physical field coupling characteristics. The proposed microfluidic pore model experiments and DEM-CFD modeling effectively elucidate microscopic mechanisms and quantify macroscopic effects, providing theoretical support for optimizing hydrate extraction strategies and ensuring reservoir stability.