Experimental investigation of cement-based sealing materials for degasification using coal-bed methane drainage system

摘要

Coal-Bed Methane (CBM) drainage system is a significant technical means for preventing disasters in the coal mines and extracting gas resources. An effective sealing of boreholes can guarantee the efficacy of CBM drainage. However, conventional sealing materials, which are utilized for CBM drainage of boreholes, exhibited several deficiencies, including autogenous shrinkage (e.g., Portland cement), poor strength (e.g., Polyurethane), high wastage rate (e.g., Mucus), etc. With respect to these weaknesses, cement-based sealing materials were prepared using cement and other additives. In this paper, the effects of the expansion sources, involving expansive agents, i.e., the content of Al powder and MgO powder, on the performance of cement-based sealing materials were investigated. In addition, the impacts of expansion field, involving the circumstance factors (i.e., water-cement ratio, temperature, and pH values) on the performance of cement-based sealing materials were assessed as well. The micro-structure and the compressive strength of cement-based sealing materials were determined and verified using a Scanning Electron Microscope (SEM) and an Electrical Universal Testing Machine (EUTM), respectively. According to the achieved results, it can be concluded that cement-based sealing materials can be widely used for determining parameters of coal seam gas, hydraulic fracturing, treating coal seam gas water injection, etc.