Review on microbial enhanced oil recovery: Mechanisms, modeling and field trials

After conventional oil recovery operations, abundant residual oil is still trapped in pore space of complex capillary network in the reservoir. As a promising method of tertiary oil recovery, microbial enhanced oil recovery (MEOR) involves the use of indigenous or specially screened microorganisms to produce specific metabolites by injecting formation or ground fermentation to enhance crude oil recovery. This paper discussed the mechanism of mobilizing trapped crude oil by microorganisms and their metabolites in detail, including interfacial tension reduction, wettability alteration, selective plugging, and degradation. Furthermore, numerical simulation for MEOR and novel technologies, such as genetically engineered MEOR (GEMEOR) and enzyme enhanced oil recovery (EEOR) were also introduced. Finally, screening criteria of reservoirs and 19 field trials cases in 9 countries were summarised. Currently, the field application of MEOR is still restricted due to the inconsistent and unstable effects and the possible negative impact of nutrient and exogenous microbial injection. However, considering the economic feasibility and environmental benefit of MEOR, it has promising application prospects in the further development of the oil fields.