Microbial Enhanced Oil Recovery: A Pore-Scale Investigation of Interfacial and Microbial Interactions Dorthe Wildenschild School of Chemical, Biological, and Environmental Engineering Oregon State University Microbial Enhanced Oil Recovery (MEOR) is a process where microorganisms are used for tertiary oil recovery. Some bacteria can facilitate the mobilization of oil through the production of amphiphilic compounds called biosurfactants that reduce the interfacial tension (IFT) between immiscible phases. Additionally, most bacteria have an inclination to colonize surfaces and form biofilm, which can change a reservoir's wetting properties or clog preferential flow paths The work under this award uses fundamental research approaches to evaluate MEOR technology, specifically biofilm- and biosurfactant- facilitated oil recovery are addressed. The MEOR mechanisms of biosurfactant production and bioclogging were studied within micromodels, using Shewanella oneidensis MR-1 that forms biofilm and Bacillus mojavensis JF-2 that produces biosurfactant and forms biofilm. Micromodel MEOR tests were visualized with a stereomicroscope to give insight into the mechanisms allowing for increased oil recovery: Test (1) Extracted biosurfactant from B. mojavensis JF-2, Test (2) S. oneidensis MR-1, & Test (3) B. mojavensis JF-2 Figure 1: Capillary desaturation curve for the abiotic recovery test in comparison to residual oil saturations for the biosurfactant and JF-2 MEOR tests. Table 1: MEOR test results for additional oil recovered, original oil in place, and residual oil saturation. Bioclogging was the most effective mechanism, in terms of AOR, compared to biosurfactant flooding and when bioclogging and biosurfactant production occurred simultaneously AOR was optimal (Table 1). Test 1 was ultimately explained by changes in capillary number where, viscosity, pore velocity and interfacial tension were mutually effected (Figure 1). In the case of biofilm formation ( Test 2 & 3, results are only for JF-2 since MR-1 biofilm was not thick enough to provide sufficient contrast for image segmentation thus biofilm induced porosity change could not be calculated) capillary number could not fully explain recovery (Figure 1) and it was assumed that a change in pore morphology, due to biofilm formation was responsible for the additional recovery.