Conclusions
Microbial activity of oil wells has a significant impact on oil recovery
efficiencies, the souring of produced oil or H2S
generation, and final oil composition. Top-down engineering approaches
via direct nutrient injection and supplementation can be used to shape
community structure and control metabolism. We validated the ability of
molasses supplemented with nitrate and/or molybdate to apply different
selective pressures which were either competitive or inhibitory of
H2S production, respectively. Molybdate supplementation
in particular provided strong selective pressure whose effects persisted
over multiple generations or passages once removed, demonstrating a
strong capacity to shape community composition and function. While these
did not enhance oil recovery in our coreflood experiments under the
conditions tested, top-down engineering had demonstrable impact on the
composition of oil recovered and inhibiting microbial souring processes.
Our work highlights the power of microbiome engineering for the
improvement of oil recovery operations and develops a workflow for the
rapid screening and evaluation of candidate oil wells.