Study Of Original Microbial Community In Different Oil Reservoirs And Construction Of Experimental System With Repect To Biofixation And Bioconversion Of CO₂into CH₄by Using Functional Genes

CO2fixation and bioconversion into CH4in oil reservoirs is a international research hotspot, and it has huge potential economic value. To further understand the microorganism involved in the process of CO2fixation and bioconversion into CH4, the petroleum reservoir production water was studied in this thesis, and the microbial community and functional genes were analyzed by molecular method. The CO2bioconversion into CH4systems were constructed through the enrichment cultures, and the microbial community composition and gas metabolites were further studied by the chemical and molecular methods combined.The functional genes invovled in the process of CO2fixation and bioconversion into CH4in four different temperature oil reservoir production water samples were researched by the molecular biology method. The results indicated that genes associated with CO2biofixation (cbbL, cbbM and FTHFS), hydrogen-producing (FeFe-hydrogenase) and methane-producing (mcrA) were all detected in the four samples, and the diversity was rich.The microbial community composition and the functional genes related to CO2fixation and bioconversion into CH4in the oil reservoir production water samples which were injected into CO2and not injected into CO2respectively were researched by the molecular biology method. The results indicated that Moraxellaceae and Pseudomonadaceae belonged to Proteobacteria predominated the bacteria in CO2injection samples, and Thermodesulfobacteriaceae belonged to Thermodesulfobacteria in non-CO2injection samples, with Methanothermobacter dominated the archaea in all the samples. cbbL, cbbM, FTHFS and mcrA genes were detected in all samples, however, FeFe-hydrogenase gene was not detected in CO2injection sample Cl.Two enrichment cultures with the oil reservoir production water as the inoculum and amended with and without NaHCO3were established and incubated under anoxic condition to construct the CO2bioconversion into CH4systems. The results showed that CH4was detected on the12th day after adding sodium acetate in the two systems, and on the120th day, the concentration of CH4were18.341mmol/L and3.13mmol/L respectively in the system amended with and without NaHCO3. Phylogenetic analyses based on16S rRNA gene showed that microbial community composition changed after enrichment culture, the preponderance of Syntrophomonadaceae and Methanothermobacter was more obvious, which indicated the systems were turning towards CO2bioconversion into CH4.Under the background of CO2fixation and bioconversion into CH4in oil reservoirs, the microbial community composition, functional genes and enrichment culture systems were researched in the present study. The results showed that there existed the variety of functional microorganisms involved in CO2fixation and bioconversion into CH4in the petroleum reservoirs, which deepened the knowledge of the microorganism involved in the bioconversion process and provided technical reference for the study and application of storaged CO2biofixation, conversion and utilization in the oil reservoirs.