Lightweight Sealing Particle Layers and Their Sealing Efficiency in CO2 Storage Reservoirs Located in Abandoned Mine Areas

Abstract

This study investigates the sealing efficacy of a lightweight particulate layer and elucidates its mechanism and efficiency in trapping CO2 within caprock fractures, thereby offering novel materials and theoretical foundations for active protection in subsurface storage reservoirs. Physical experiments were conducted using a custom-designed CO2 sequestration visualization apparatus, complemented by comparative analyses through COMSOL numerical simulations. Three types of lightweight particles─polystyrene foam, hollow glass microspheres, and a foam glass microsphere mixture─were employed to seal caprock fractures. The study systematically examined the morphological characteristics, stability, and CO2 sealing efficiency of the resulting sealing layers under varying particle conditions. Experimental results indicate that (1) lightweight particles, due to their low density, readily bridge and obstruct fracture throats under CO2 fluid pressure, forming stable “particle-blocking layers”, and (2) injection of CO2 mixed with blocking particles effectively reduces leakage rates and extends leakage duration. Under the selected conditions, all three particle types significantly decreased CO2 leakage rates, achieving reduction efficiencies of 84.9%, 84.8%, and 84.7%, respectively, relative to the unmodified system. These findings confirm that lightweight particle sealing layers constitute an efficient and stable active sealing technology for fractures in CO2 storage reservoirs within abandoned mine workings. The results provide theoretical support and critical experimental evidence for the design and safe operation of sealing strategies in such storage reservoirs.