Biosystem development for microbial enhanced oil recovery (MEOR)

Abstract

Conventional primary and secondary oil recovery processes recover only one third of the oil present in the oil reservoir. EOR technologies produce an additional oil recovery after these processes cease to produce oil. Microbial enhanced oil recovery (MEOR) includes the tertiary oil recovery process where microorganisms or their metabolites are used to retrieve the unrecoverable oil from oil reservoirs. Oil recovery mechanisms facilitated by microorganisms are attributed to the metabolites produced by them. Biosurfactants, biomass, biopolymers, solvents, acids, gases, etc. are notably the products of microbial growth in the reservoir. MEOR approaches are either in situ or ex situ. In in situ approach growth of the indigenous microbes is stimulated or isolated microbes having specific traits are injected into oil reservoir along with the nutrients where production of the metabolites causes oil release. The approach where microbes are cultivated outside in a fermentor on inexpensive raw materials and they and/or their crude metabolites, viz. biosurfactant, biopolymer, etc. are injected into oil reservoir in order to retrieve the unrecoverable oil, is known as ex situ oil recovery. The technical feasibility of oil recovery was assessed in porous model sand packed columns with biosystems developed separately comprising of the specially isolated B. licheniformis TT42, K125 and TT33. The crude biosurfactant of B. licheniformis K125 gave 43 ± 3.3% additional oil recovery upon application to sand column which is 13.7% and 8.5% higher in comparison to the standard strains, Bacillus mojavensis JF-2 and Bacillus licheniformis TT42 respectively. B. licheniformis when tested in sand packed column by injecting the biomass and the nutrients gave 27.7 ± 3.5% oil recovery. Lack of holistic approach allowing for a critical evaluation of economics, applicability and performance of MEOR is missing. For a thorough assessment of this process a multidisciplinary approach is warranted.