Investigation on behavior of bacteria in reservoir for microbial enhanced oil recovery

Behavior of bacteria activated in reservoir through molasses-injection-test s, was investigated using the restriction fragment length polymorphism anal ysis with the polymerase chain reaction (PCR-RFLP) method, for elucidating potential bacteria to suppress in situ growth of microbes to be injected in to the reservoir in the microbial enhanced oil recovery (MEOR) process. As a result, some bacteria belonging to Enterobacteriaceae species or their cl ose relative species were grown predominantly in the reservoir, among bacte ria inhabiting in the ground-water. The foregoing indicates that behavior o f these bacteria in reservoir must be taken into consideration when giving a full account of behavior of microbes to be injected into the reservoir to put the MEOR process into operation. Potential proliferation using molasses to activate those bacteria was also estimated on the laboratory tests, to clarify the indispensable conditions for effective and competitive in situ growth of microbes to be injected int o the reservoir to operate the MEOR process. In consequence, it became clea r that these bacteria have a potential growth exceeding 10(8) CFU/ml, utili zing molasses. These facts indicated that microbes to be injected into the reservoir at the MEOR field tests are necessary to grow more excellently th an bacteria inhabiting in the ground-water. In addition, as flow, the injec tion fluid is influenced by reservoir heterogeneity caused by injection of molasses, it was inferred that microbes to be injected into the reservoir a t the MEOR field process are also necessary to grow more remarkably than ba cteria inhabiting in the reservoir brine at high permeability zones and bac teria inhabiting in the reservoir rock. Furthermore, the results of the functional testing for MEOR conducted in th e presence of bacteria activated through molasses-injection-tests indicated the importance of effective use of microbes to be injected, taking into ac count the characteristics of the reservoir and function for MEOR of those m icrobes.