Study On Migration Characteristics Of The Leaked Hydrogen Sulfide From Cracked Oil/gas Wells Penetrating Longwalling Mining Areas And Its Control By Injecting Lye

With the gradual depletion of coal resources in the eastern mining areas of my country,the focus of coal resource development has gradually shifted to the northwest.Coal-oil and gas superimposed mining areas represented by the Ordos Basin,the Junggar Basin,and the Tarim Basin are facing many problems in the coordinated development of multiple resources.Among them,the Shuangma Minefield in the Majiatan mining area on the western edge of the Ordos Basin overlaps vertically with CNPC’s"Hujianshan Oil and Gas Exploration in the Ordos Basin,Shaanxi,Ningxia,and Mongolia"block.There are a large number of coal,oil,natural gas and other resources in this area.The development of oil and gas resources was earlier than coal,which resulted in a large number of abandoned oil and gas wells left in the later well fields.Since the early oil and gas wells were not installed with casings,various gases such as natural gas and oil layer associated gas（hydrogen sulfide,etc.）Rock fissures move to the mining face,which brings great risks to coal mining.In particular,hydrogen sulfide in oil and gas wells is a highly toxic gas,which poses a serious threat to the life and health of underground workers and the service life of equipment.Based on the working face of Shuangma Coal MineⅠ0104105 as the research background,through literature research,field measurement,theoretical analysis and calculation,numerical simulation and other means,the characteristics of hydrogen sulfide leakage in the coal-oil-gas cross mining area are analyzed;the hydrogen sulfide leakage from abandoned oil and gas wells is studied The spatio-temporal migration law of the intruded coal seam;and for this purpose,the numerical simulation research on the treatment of hydrogen sulfide by alkali injection and sulfur fixation in coal seam was carried out.The research results can provide a certain theoretical basis for the prevention and control of hydrogen sulfide and other harmful gas disasters in this area.The main research content and results of the thesis are as follows:（1）Through literature research and on-site measurement,the migration pathway and enrichment characteristics of hydrogen sulfide leaked into the coal seam in the coal oil and gas cross-mining area are clarified;Carrying out theoretical research on high-pressure alkali injection and sulfur fixation in coal seams provides a theoretical basis for the subsequent construction of multi-physical field coupling models and numerical simulation studies for alkali injection and sulfur fixation in coal seams.（2）Based on the laws of mass conservation and energy conservation,considering the effective stress change and adsorption expansion deformation of coal seams caused by hydrogen sulfide gas intrusion into coal seams,a stress-seepage coupling model for hydrogen sulfide intrusion into coal seams from abandoned oil and gas wells in the coal-oil-gas cross mining area was constructed.Solved by the multiphysics field coupling software COMSOL Multiphysics,the temporal and spatial migration laws of hydrogen sulfide leaked from abandoned oil and gas wells into coal seams are revealed.The simulation results are compared with the field measured data to verify that the two are in good agreement.（3）Based on the coal damage caused by the coal seam fluid system and stress changes during the high-pressure caustic soda injection in the coal seam,a stress-seepage-chemical multi-physics field coupling model was constructed,combined with the diffusion of leaked hydrogen sulfide in the coal seam determined by the previous simulation Radius and the actual distribution of hydrogen sulfide concentration in the coal seam of the I0104₁05working face,the multi-physics field coupling simulation of the coal seam injection sulfur fixation process was carried out,the diffusion range of the alkali solution in the coal seam at different alkali injection pressures was studied,and the optimal alkali injection pressure was determined.and time;further simulated the absorption effect of hydrogen sulfide in the coal seam under the single-hole and multi-hole arrangement,compared and analyzed the monitoring data of the field test and the numerical simulation results,and finally optimized the parameters of the alkali injection of the coal seam,which provided a reasonable implementation of the technical measures for on-site engineering prevention and control.Provides useful support.There are 57 figures,8 tables and 91 references in this thesis.