Research and application progress of liquid-based sealing materials for gas drainage boreholes

Coal mining is gradually entering the stage of deep exploitation. The significant increase in mining depth further enhances high in-situ stress, and coupled with effects such as mining-induced stress relief, the rock mass surrounding gas drainage boreholes in deep coal seams is more susceptible to plastic failure, accompanied by severe propagation of micro-fractures, resulting in a rapid attenuation of coal seam gas drainage efficiency. Against this backdrop, the shortcomings of traditional solid-phase sealing materials for gas drainage boreholes have been gradually revealed. Over the years, extensive technical improvements have fully exploited the potential of the "solid sealing for gas" technology, and its effectiveness has reached its limit. Liquid-based sealing materials, with their excellent rheological properties, exhibit significant advantages in deep penetration into micro-pores, tight adhesion to borehole wall interfaces, adaptation to dynamic fracture evolution, and strong self-deformability, making them a research hotspot in the field of sealing materials in recent years. This paper systematically reviews the physicochemical properties and sealing mechanisms of various liquid-based sealing materials, summarizes three typical systems, namely bentonite-based suspensions, silicate-based gels, and resin-based modified solutions, and elaborates on the composite enhanced sealing mechanisms involving rheological regulation, fiber toughening, and particle support. Based on typical engineering cases, this paper demonstrates the excellent engineering performance of liquid-based sealing materials in improving gas drainage concentration and prolonging borehole drainage duration. Meanwhile, it identifies the key issues that need to be addressed in aspects such as precise stability control, long-term durability, and visual evaluation. Finally, it clarifies that the integrated technical path, which is based on the micro-fracture filling mechanism, centered on material rheological regulation, and supported by visual monitoring equipment, represents the future development direction of this field. The research findings provide a technical reference for the application of liquid-based sealing materials in gas drainage sealing under deep and complex geological conditions.