Microbes enhance oil recovery through various mechanisms

Oil operators employ microbial enhanced oil recovery (MEOR) methods, which use microorganisms and nutrients to mobilize residual oil, to enhance oil recovery. Certain bacteria are capable of generating surfactants, polymers, gases, and solvents that facilitate mobilization of residual oil in an oil reservoir. Surfactants decrease oil-water interfacial tension (IFT), while capillary pressure, which is proportional to IFT between oil and water, holds the residual oil in porous rocks. Certain bacteria generate gas and solvents in the reservoir, which can dissolve in crude oil and decrease crude oil viscosity, resulting in an enhanced mobility ratio and oil recovery. Certain bacteria are capable of degrading the paraffin contents in crude oil, thus improving permeability and production rate of the wellbore region. Operators can inject bacteria solution into the reservoir through production tubing in an oil generating well. Other bacteria can produce polymers that seal high-permeability channels in porous media.