Microbial Community Evolution And Gas Water Interaction Mechanism In The Process Of Producing Water From Coalbed Methane Wells

In this paper,about 18 CBM development wells are selected as research objects in Western Guizhou.Based on the results of convertional ions,trace elements,hydrogen and oxygen isotopes,dissolved inorganic carbon isotopes,16 S r RNA sequencing in produced water,components and methane and hydrocarbon isotopes in produced gas.The evolution characteristics of geochemical indexes of drainage water and gas and the evolution characteristics of microorganisms in prodeced water with time and space are analyzed.The interaction relationship between microbial community and produced water and gas in the process of drainage is discussesed.The microorganisms were used to identify the pay zones of CBM wells,and the potential of bioaugmentation methane production in the study area is evaluated.The main understandings are as follows:The temporal variation characteristics of geochemical indexes of produced water and gas are discussed,and the spatial variation characteristics of geochemical indexes of produced water and produced gas in different drainage time are analyzed.The chemical indexes of produced water in Laochang and Enhong areas of eastern Yunnan changed sharply with time,and the source of produced water was the transition from fracturing fluid pollution to original coal seam water.The chemical indexes of produced water in Songhe and Faer areas with longer drainage time are relatively stable with drainage time,and the source of produced water is characterized by pressure fracturing fluid pollution.With the change of drainage time,the change range of Laochang and Enhong areas in eastern Yunnan is larger than that of Songhe and faer areas in western Guizhou.In the GP well group of Songhe area where the inter well interference has been formed,the water chemical indexes of CBM wells with deeper target buried depth are higher.The evolution characteristics of archaea and bacteria community structure with time and space in the produced water of coalbed methane wells in the study area are revealed,and the changes of microbial community structure before and after anaerobic culture in the laboratory are discussed.Seven archaea phyla were detected,and the richness and diversity of archaea community decreased with the change of drainage time.Eleven phyla were detected,among which Proteobacteria had the highest relative abundance,and the bacterial community was mainly oligotrophic and chemotrophic.With the increase of burial depth,the richness of archaea community gradually increased,and the richness and diversity of bacterial community also increased with the increase of burial depth.In Songhe and Enhong areas,hydrogen trophic methanogens were dominant.Anaerobic enrichment culture in laboratory is beneficial to the growth of Archaea community.In the process of drainage time,the relationship between the geochemical characteristics of produced water and produced gas and the microbial community structure in the produced water was analyzed,the method of identifying productivity contribution by using microbial community composition was proposed,and the evaluation of microbial enhanced methane production potential was evaluated.Compared with Archaea community,bacterial community is more sensitive to the change of hydrochemical environment.When Cl-,Na+,TDS representing the rapidly changing water environment decreased,the abundance of Archaea decreased.According to the composition of Archaea community in the produced water,the contribution of the production layer can be preliminarily judged.The development horizons of Songhe and Enhong have good geological conditions for the existence of methanogenic bacteria,which is suitable for carrying out the engineering experiment of microbial enhanced methane production by injecting nutrient solution in the later stage.