About this Research Topic
Although non-traditional energy sources such as bioethanol, solar, and wind will increase over the coming decades, it is predicted that these will account for less than 10% of total demand by 2030. As such, global reliance on fossil energy will likely continue to dominate even as oil supplies dwindle. As we move into an era focused on limited conventional fossil fuel reserves there is renewed interest in the microbiology and biogeochemistry associated with oil fields and their operation. This is because microbial processes can be both detrimental and beneficial to oil recovery. Detrimental processes include (i) natural and inadvertent stimulation of biodegradation of light oil components leaving a heavy oil residual of lower value that is logistically difficult to recover; (ii) hydrogen sulfide production due to inadvertent in-situ stimulation of sulfate reducing microorganisms during oil recovery, which poses significant health, environmental, and corrosion threats; and (iii) direct and indirect corrosion through the activity of multivariate microbial processes in pipeline and field equipment biofilms. New areas in these fields include a better understanding of natural processes surrounding hydrocarbon biodegradation and H2S biogenesis; new inhibitors for souring control; and new developments of the role of direct electron transfer mechanisms in microbially induced corrosion.
Beneficial microbial processes are based on the application of microbiology to enhance oil recovery in an environmentally and economically favorable manner. Microbial enhanced oil recovery (MEOR) uses various microbial metabolisms to increase hydrocarbon and energy yield by improving oil flow and reservoir floodwater sweep. MEOR strategies can include processes that alter reservoir matrix lithology, floodwater flow, floodwater or oil viscosity, oil chemistry, or in-situ pressure driving oil out. These effects are based on the ability of microorganisms to (i) to produce acids, alkalis, or ligands that indirectly weather rock; (ii) to produce gases, biosurfactants, or polymeric substances, which alter floodwater and oil viscosity and fluid characteristics improving sweep efficiency; (iii) to form biomass which alters rock permeability to floodwaters improving sweep volume; and (iv) to biotransform components of crude oil into lighter molecular structures making the oil more inviscid. Although much is known of these individual metabolisms under benign conditions, little knowledge exists of these processes in high pressure, hypersaline, and hyperthermal environments typical of oil fields or of the community effects or environmental parameters that control the activities of the relevant species. New and exciting aspects of MEOR are based on the direct microbial neogenesis or diagenesis of rock minerals through oxidative and reductive reactions resulting in significant alteration in matrix porosity.
This Research Topic aims to gather contributions from scientists working in diverse disciplines with common interests in key areas of oil reservoir biogeochemistry. We want to highlight modern approaches to studying microbial interactions with each other and rock matrices, hydrocarbons, sulfur species, and metals in the oil reservoir environment. Both abiotic and biological processes contribute to biogeochemical cycles in the context of the reservoir environment requiring a comprehensive mechanistic understanding involving integration of studies at the field scale with studies at the microbial and molecular scales.
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