The Study Of Genesis Modes And Enrichment Control Factors Of Hydrogen Sulfide In Huayingshan Coal Mining Area

Sichuan is known for its high sulfur content in the country.In the Huayushan mining area,there have been a number of accidents of abnormal hydrogen sulfide emission.Therefore,it is of great significance for the prevention and control of H₂S in the mining area that the controlling factors of H₂S genesis and anomalous gushing in the Huayingshan mining area.The paper takes the Huayingshan mining area as the research object,and applies analysis methods such as geochemistry,coalbed methane geology and gas geology to analyze the coal industrial analysis,sulfur isotopes,vitrinite reflectance,fluid inclusions,etc.Research on the genetic types of hydrogen sulfide and geological control factors in the study area has achieved the following understanding:Huayushan Mining Area main coal seam is Permian Longtan Formation.The degree of deterioration of coal is high,Low-volatile,medium-ash,and high-sulfur bright coals are the main deposits,which belong to the interactive marine and terrestrial deposition.Total sulfur content greater than 3.00%.The composition of sulfur in mine coal is pyrite sulfur,which accounts for more than 70%of total sulfur,followed by organic sulfur,and the content of vitrinite in coal is high,with an average of 74.9%.Affected by seawater,there was a corresponding negative correlation between volatiles and ash yields with total sulfur content.The microscopic morphology is columnar pyrite crystals filled in coal seam fissures and in the cavities of coal rock organic matter.Based on the characteristics of coal seam gas,H₂S content,vitrinite reflectance of coal,fluid inclusions,carbon and sulfur isotope characteristics,and chemical characteristics of water,the content of hydrogen sulfide in the mining area is high.The vitrinite reflectance of coal is mainly from 0.71%to 1.65%,and the homogenization temperature of fluid inclusions is between 116°C and 211°C,which indicates that the coal rocks have experienced deposition temperatures more than 120°C.The pyritic sulfur isotopes of the high-sulfur coals in the Longtan Formation are mainly from+9.45‰to+38.40‰,the H₂S sulfur isotope distributions in coal seam gas and natural gas are mostly from+6.1‰to+20‰,and the?³⁴S values of the anhydrite in the formation are mainly from+12.0‰to+26‰.In short,the sulfur isotopes of H₂S is lighter than anhydrite and pyrite.The carbon isotopic composition of methane among the coal seam gas and natural gas in the studied region is mostly-33‰to-30‰,and the carbon isotopic of ethane is mostly-33‰to-28‰.The carbon isotope is generally weighted.In the flow direction,salinity of underground water have an decreasing trend.All showed the characteristics of TSR.It is concluded that H₂S in coal mine is mainly generated by TSR,but genesis ofBSR in partial region cannot be excluded.The source rock of the Longtan formation in the Permian of the main coal seam has a high organic matter abundance,and the hydrocarbon generation intensity is more than20×10⁸m³/km²,which provides a solid material basis for the TSR action of H₂S.The reservoir of the mining area has good storage properties.The roofs and floors in each coal seam are mainly composed of the fine clastic rocks,together with the low permeability layer,which are not conducive to emission of H₂S.The rock formation is an efficient combination of generation,storage,and capping of hydrogen sulfide.Aquifer has strong water-concentration so that there is danger of water gushing-out.At the same time,a drainage channel was opened to remove the blocking effect of surrounding rocks on gases such as gas and H₂S so that the free hydrogen sulfide in the coal and rock layers would flow out.