Study on the characteristics of surrounding rock sealing materials under the background of CO2 escape in geological sequestration of abandoned mine

Abstract

Abstract Geological carbon dioxide sequestration as a key approach to energy preservation and emissions reduction has garnered attention among scholars in recent years. The abandoned coal mine contains expansive caving areas and abandoned roadway chambers, presenting a promising opportunity to repurpose the site as a carbon dioxide geological storage facility. Nonetheless, numerous micro-cracks are present in the surrounding rock of the abandoned mine roadway, particularly in the goaf. Under high-pressure seepage conditions resulting from long-term geological storage, micro-cracks will continue to fracture and expand, forming channels through which CO2 can escape. To address the aforementioned issues, this study conducted tests on superfine cement grout's properties and determined its rheological and stability characteristics based on varying particle sizes and different quantities of superfine fly ash, superfine silica fume, and high-efficiency water-reducing additives. The sensitivity factors were analyzed through an orthogonal test, leading to proposing the optimal ratio of ultrafine fly ash, ultrafine silica ash and high efficiency water reducing agent. This provides a foundation for selecting the slurry sealing performance of CO2 geological storage surrounding rock.