MEOR Strategies
Changing oil reservoir ecophysiology to favour MEOR can be achieved by complementing different strategies. In situ microbial stimulation can be chemically promoted by injecting electron acceptors such as nitrate; easy fermentable molasses, vitamins or surfactants. Alternatively, MEOR is promoted by injecting exogenous microbes, which may be adapted to oil reservoir conditions and be capable of producing desired MEOR agents (Table 1).
| MEOR agents | Microbes | Product | Possible MEOR application |
| Biomass, i.e. flocks or biofilms | Bacillus sp. | Cells and EPS (mainly exopolysaccharides), | Selective plugging of oil depleted zones and wettability angle alteration |
| Leuconostoc | |||
| Xanthomonas | |||
| Surfactants | Acinetobacter | Emulsan and alasan | Emulsification and de-emulsification through reduction of interfacial tension |
| Bacillus sp. | Surfactin, rhamnolipid, lichenysin | ||
| Pseudomonas | Rhamnolipid, glycolipids | ||
| Rhodococcus sp. | Viscosin and trehaloselipids | ||
| Arthrobacter | |||
| Biopolymers | Xanthomonas sp. | Xanthan gum | Injectivity profile and viscosity modification, selective plugging |
| Aureobasidium sp. | Pullulan | ||
| Bacillus sp. | Levan | ||
| Alcaligeness sp. | Curdlan | ||
| Leuconostoc sp. | Dextran | ||
| Sclerotium sp. | Scleroglucan | ||
| Brevibacterium | |||
| Solvents | Clostridium, Zymomonas and Klebsiella | Acetone, butanol, propan-2-diol | Rock dissolution for increasing permeability, oil viscosity reduction |
| Acids | Clostridium | Propionic and butyric acids | Permeability increase, emulsification |
| Enterobacter | |||
| Mixed acidogens | |||
| Gases | Clostridium | Methane and hydrogen | Increased pressure, oil swelling, reduction of interfacial section and viscosity; increase permeability |
| Enterobacter | |||
| Methanobacterium | |||
This knowledge has been obtained from experiments with pure cultures and some times with complex microbial communities but the experimental conditions are far from mimicking those ones prevailing in oil reservoirs. It is unknown if metabolic products is cell growth dependent, and claims in this respect should be taken cautiously, since the production of a metabolite is not always dependent of cellular growth.
Read more about this topic: Microbial Enhanced Oil Recovery
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