Figure 5 – Top-down nutrient formulations control microbial metabolism in ways the affect both oil yield and composition. A) Overview of mini-coreflood (MCF) experimental design where cores are saturated with oil, accessible oil (primary recovery) is extracted with brine and microbes are seeded with produced water, nutrients are subsequently injected, and reactors are shut-in for ten days before they are vented and flooded with brine to recover any of the oil liberated by the microbial processes (i.e. secondary recovery). B) MCF experimental setup showing the pump which injects either oil, sterile brine, well water for seeding, or nutrient supplements with the MCF canisters encasing the core material and C) an actual image of assembled MCF apparatus. D) Pressure generated during 10 day mini-coreflood by various supplements. E) Chemical composition of produced oil after microbial mini-coreflood. F) Fraction of residual oil in place that was recovered after 10-day microbial shut-in period. G) Composition of microbes in effluent from the microbial mini-coreflood after 10-day shut in period. This data represents one trial which is the most data complete, a replicate performed at a different time from different produced water is presented in the supplement (Supplemental Figure 8).