Study On Characteristics Of Gas Occurrence And Distribution Of Residual Gas After Drainage In Hudi Mine

This paper takes the Hudi coal mine as the research area and the coal seam as the research object.The characteristics of structural development and gas occurrence in the Hudi Mine are summarized and analyzed.Based on the observation of coal,rock joints and micro-fractures and permeability experiments,the characteristics of fracture development and permeability of coal reservoir in the study area are discussed.The characteristics of gas occurrence in 3~#coal seam are analyzed and the influence of geological conditions on gas accumulation is discussed.The gas extraction similar simulation test device is designed and the extraction experiment is carried out in combination with the geological conditions in the study area.The dynamics of residual gas distribution is analyzed,and the distribution law of residual gas and its geological control are discussed.The gas content of 3~#coal seam is 14.67~40.12 cm~3/g,and the gas content in the whole is relatively high.According to the analysis of the gas occurrence conditions,the coal seam burial depth is the main controlling factor of gas occurrence,and the gas content increases with the increase of the buried depth,and the factors such as collapse column,fault and coal thickness have a local influence on the gas content.The density of joints in coal seam is mainly Article 2~18m,which shows the trend of"north high and south low".The development law of joint density is consistent with structural deformation,and the density of joint develops higher in fold axis.Low density of joints far away from fold axis;The density of micro fissures is positively linearly correlated with the density of joints,and the variation trend of them is consistent.The density of micro fissures in coal seam is0.5~4.5mm/mm~2.;The change range of permeability of coal seam is 0.01~0.64mD.permeability and lateral pressure coefficient show a negative exponential function relationship,but have a positive exponential relationship with micro-fracture surface density.Residual gas content is mainly affected by in situ gas content,structure,fracture density,coal thickness,buried depth and so on.Through grey correlation analysis,it is concluded that the degree of influence of local quality factors on residual gas content is as follows:in situ gas content,buried depth,fracture surface density,structure and coal thickness.Residual gas content is positively correlated with in-situ gas content,buried depth,structural complexity and coal thickness,and negatively correlated with fracture surface density.The similar simulation test device is mainly composed of the sample box,the inflatable device,the extraction device,the data acquisition device,the simulated coal seam and the stress loading device,which can study the law of dynamic change of gas content in the process of drainage.The similarity simulation analysis shows that the residual gas content has a negative exponential function relationship with the extraction time,and the dynamic change characteristics of the gas content are determined by three factors:ground stress,gas pressure and borehole location.In the early stage of extraction,the gas pressure is the main control factor,and in the later stage,the stress is the main factor,while the location of the borehole acts on the whole process of gas extraction,and the residual gas content,the in-situ stress and the distance between the residual gas content and the in-situ stress.The borehole distance is positively correlated.