Research and application of CBM surface extraction based on coal mine with “gas drainage first, construction later” and resource development

Aiming at the safety index put forward by "gas drainage first, construction later" of coal mine at present and the resource characteristics of many coal seams in northern Guizhou Province, and at the same time making up for the lack of systematization and large blind area of surface gas drainage deployment at present, this paper took Duijiangnan coal mine as an example to carry out the research of coal bed methane surface drainage deployment. Based on the complex topographic conditions, coal seam development characteristic(multiple layers, thin thickness, group distribution), coal body structure, development and deployment requirements in this area, the development mode of horizontal wells with segmented fracturing and cluster wells was optimized. Four horizontal well groups and 16 vertical wells(cluster wells) were deployed along No. 1 and No. 2 working faces, occupying 7 well sites. Through the establishment of fine geological model and grid division, CBM-SIM numerical simulation software was used to simulate the average daily gas volume of surface drainage in 20 wells(well groups) during 5 a, which can reach 26 036.54 m³, and the CBM content of seam M78 in No.1 and 2 working faces decreased by more than 30% after 5 a gas drainage. The simulation results show that the fine deployment of well location in Duijiangnan coal mine can effectively reduce the gas content in the working faces and give consideration to the dual purposes of coal mine safety production and utilization of CBM resources. This method can provide a new idea and method for the coordinated development of coalbed methane through surface extraction and underground mining safety.