Study On The Characteristics Of Produced Water And Microbial Species Of Coalbed Methane Wells In Shizhuangnan Block,Qinshui Basin

The Qinshui Basin is the main area for coalbed methane mining in my country,and the Shizhuangnan Block is one of the important development blocks in the Qinshui Basin.For a long time,questions about the existence of microorganisms in the Shizhuangnan Block,whether microbial gas was produced,and why can't it be detected if microbial gas is produced,have not been well answered.This paper takes Shizhuangnan Block in Qinshui Basin as the research area.Select the CBM(coalbed methane)well in the No.3 coal seam in the area,collect its produced water samples,determine the concentration of conventional ions(Na⁺,K⁺,Ca²⁺,Mg²⁺,Cl^-,CO₃^2-,HCO₃^-,SO₄^2-plasma),and analyze the production of CBM wells.Type of water production;use the isotope data of the produced water and gas samples of coal-bed methane wells to analyze the chemical characteristics of the produced water of the coal-bed methane well.The water hydrogen and oxygen isotope data are used to identify the source of the produced water,and the dissolved inorganic carbon isotope data in the water is used to determine the existence of biogenic gas,the dissolved CH₄ isotope and CO₂ isotope in water are used to determine the genetic type of water-soluble methane,and the gaseous CH₄ isotope is used to determine the genetic type of methane in the produced gas;16S r RNA sequencing technology is used to determine the water produced by coalbed methane wells The characteristics of the microorganisms in the sample,determine the type of microbial species and main bacterial species in the study area;study the reaction mechanism of bacterial species that play an important role in the biogeochemical cycle,including methanogens and methanobacteria related to the C cycle,and Sulfate reducing bacteria related to the S cycle and denitrifying bacteria related to the N cycle explain the genetic types of methane in the study area;combine the hydrogeological conditions of the study area with the water ion and isotope characteristics of coalbed methane wells in different hydraulic zones to identify coal Microbial characteristics and geochemical response of reservoir water production.The research results show that the water produced by the CBM well in the No.3 main coal seam of Shizhuangnan Block is mainly Na-HCO₃ type,and Na-HCO₃-Cl type is less common.The main source is the atmospheric precipitation replenishment received at the eastern outcrop;The main geochemical processes in the coal seam are cation exchange and sulfate reduction,and the secondary geological process is carbonate dissolution;the main species of microorganisms in the study area at the class level are Betaproteobacteria,Gammaproteobacteria,Alphaproteobacteria and Flavobacteriia,at the genus level The main species are Hydrogenophaga,Flavobacterium,Pseudomonas,Methylobacte and Acinetobacter;methanogens,methanobacteria,sulfate-reducing bacteria,and denitrifying bacteria in the study area are all distributed in the western part of the study area(deeper part of the coal seam),and the abundance in the middle area The distribution of sulfate-reducing bacteria is opposite to that of SO₄^2-concentration,the distribution of sulfate-reducing bacteria is opposite to that of NO₃^-,and the distribution of dissolved inorganic carbon isotope is the same as that of methanogens.Consistent;methanogens did perform methanogenesis and produced CH₄ with a lighter isotope,but methanotrophic bacteria were widespread in the western part of the study area,and their abundance was significantly greater than that of methanogens.The biogenic CH₄ was methanotrophic.It is difficult to preserve due to oxidation,so the biogenic gas was detected in the study area,but the geochemical indicators of the produced gas only showed that the gas of thermal origin.