Microbes enhance oil recovery through various mechanisms

The first part of a series on microbial enhanced oil recovery (MEOR) applications is presented. MEOR methods rely on microorganisms and their metabolic products to mobilize residual oil in several different ways. Oil and gas exist in porous rocks at depths from several hundred to several thousand meters. In the early life of an oil field, the reservoir pressure is high and oil and gas flow to the wellbore naturally. Operators employ tertiary recovery or enhanced oil recovery methods to produce residual oil. Most common EOR methods include surfactant flooding, polymer flooding, CO2 flooding, and thermal recovery. MEOR methods have many distinguishable advantages. It is environmentally friendly because it does not involve toxic chemicals. Operators can also inject bacteria and nutrient into a reservoir from an injector and then continue normal waterflooding operations. In the more common huff-and-puff operations, bacteria only treat the near-wellbore region of producers, while bacteria flooding transports bacteria deep into the reservoir.