Advances in production related petroleum microbiology.

The understanding of microbial diversity and their metabolic activities inside the oil reservoir is not well understood. The microbial community of the oil reservoir plays diversified roles from souring to microbial enhanced oil recovery. Therefore, studying community dynamics, phylogenetic diversity and ecological roles of the community inside the reservoir is crucial. This chapter discussed different microbial processes taking place in petroleum reservoirs. The study showed the crude oil being the major electron donor inside the reservoir supporting major life forms. The major metabolic reactions taking place are nitrate and nitrite reduction, sulfur and sulfate reduction, iron reduction, fermentation, and methanogenesis. Many of the thermo-tolerant strains that are capable of exploiting numerous energy sources and electron acceptors are among the most often cultured on functional groups, which include sulfate and sulfur reducing bacteria like Desulfacinum infernum, Desulfacinum subterraneum, iron reducing, fermentative such as Thermococcus, Thermotoga, and Thermoanaerobacter species, and methanogenic microorganisms like Methanothermobacter thermautotrophicus. The stimulated growth of microbes could also enhance the oil recovery from the reservoir by 66 percent as proved in some experimental studies. The microbial growth could be increased by injection of nitrate which could also control sulfide production, or nutrients such as sugar molasses that increases fermentative microbial growth, which could improve volumetric sweep efficiency and thus oil recovery. Microbial growth also has the potential for corrosion and souring due to the presence of microbes such as Desulfovibrio¸ Clostridium etc. It could be concluded that the scope of microbial diversity is far more extensive than what is known till date.