Research On Gas Enrichment Mechanism Of Roof Limestone In No.8 Coal Seam,Shenzhou Coal Industry,Shanxi

The gas in the roof limestone(L1)of the No.8 coal seam in Shanxi Shenzhou Coal Industry is abnormal,which has an important impact on coal mine safety production.In this paper,based on the study of regional geological background and the characteristics of coal measures and reservoirs,combined with relevant experimental testing methods,the origin,source and enrichment mechanism of L1 limestone gas are studied to provide a theoretical basis for coal mine gas prevention.The research methods adopted and the main research results obtained are as follows:Firstly,the physical properties of L1 limestone samples were tested by SEM,mercury intrusion,rock pyrolysis and isothermal adsorption.The experimental results show that the pores of L1 limestone are mainly micropores and transition pores,which are relatively dense.The organic carbon content and hydrocarbon generation potential of L1 limestone are very low,there is no possibility of independent hydrocarbon generation,and the adsorption capacity for gas is very low.Secondly,the water ion concentration,hydrogen and oxygen isotopes of the limestone of the Taiyuan Formation,the carbon and hydrogen isotope characteristics of the main coal seam and the gas sample of the L1 limestone,and the microbial community of the L1 limestone water sample were studied and analyzed.In L4,L1,L4 limestone water are all supplied by atmospheric precipitation,there is no hydraulic connection between the two;L1 limestone water samples detect desulfurization bacteria that can only survive under anaerobic conditions,confirming that L1 roof limestone water is in The closed reduction environmental conditions,on this basis,according to the gas and hydrocarbon isotopic characteristics of the gas samples collected to obtain L1 limestone gas genesis type.Combining the characteristics of hydrogen and oxygen isotopes in water samples,hydrogeological conditions and coal system stratum space combination characteristics,the source of L1 limestone gas is obtained.Finally,through the analysis of the structural evolution history of the study area,combined with the impact of the limestone reservoir characteristics,structural characteristics,depositional conditions and hydrogeological conditions on the L1 limestone gas enrichment,the L1 limestone gas enrichment Model,expounding its enrichment mechanism.Qualitatively predict the areas where the gas concentration of Shenzhou Coal Industry needs to pay attention to through grey correlation analysis,and according to the enrichment characteristics of L1 limestone gas,put forward the prevention and control suggestions for gas outburst.