Study on genetic and destructive mechanism of gas from surrounding rock in Huangling Mining Area

As the mining process of coal mines (e.g. No.2 Huangling Coal Mine) in Huangling Mining Area along the southern margin of Ordos Basin, a great amount of gas flows comes from the surrounding rocks underground, leading to mining suspension and serious threat to the safe production of coal mines.Based on the geochemistry parameters of gas samples from coal surrounding rock, the geological structure and sedimentary characteristics of Huangling Mining Area.Source rock correlation, identification of oil type gas and numerical simulation methods are used to reveal the source and migration pathway of gas from coal surrounding rock. Further, the mechanism of disaster occurrence under mining disturbance is also discussed. The results show that the gas from coal surrounding rock is a typical oil type gas associated with pyrolysis of crude oil which are discriminated by the average value of δ13C2 is lower than 2.88% and Schoell Plate analysis, the roof gas sandwiched with a small amount of coal gas and oil gas mixture.The genetic mechanism of the gas from coal surrounding rock in the study area is mainly from the source rock of Yanchang Formation, transporting to floor rock at the first with migration pathway of fissure channels formed by basement structures, transporting form bottom to coal seam and roof by the sandstone reservoir and epigenetic fissure providing the secondary migration pathway for the bottom oil type gas.Due to mining disturbance, the balance of original stress and completeness of surrounding rock was broken that formed the transport channels of gas, through these channels, accelerating the abnormal emission happens under the comprehensive catalysis of gas pressure. These factors lead to the occurrence of surrounding rock gas disaster.