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MEOR Site |
Microbial Enhanced Oil Recovery (MEOR) relies on microbes to ferment hydrocarbons and produce a by-product that is useful in the recovery of oil. MEOR functions by channeling oil through preferred pathways in the reservoir rock by closing/ plugging off small channels and forcing the oil to migrate through the larger pore spaces. Nutrients such as sugars, phosphates, or nitrates frequently must be injected to stimulate the growth of the microbes and aid their performance. The microbes generate surfactants and carbon dioxide that help to displace the oil.
Microbial growth can be either within the oil reservoir (in situ) or on the surface where the byproducts from microbes grown in vats are selectively removed from the nutrient media and then injected into the reservoir. For in situ MEOR processes, the microorganisms must not only survive in the reservoir environment, but must also produce the chemicals necessary for oil mobilization.
DOE has been a leader in the development of microbial technology. In addition to funding research in the United States, DOE has participated in cooperative technology exchange internationally.
DOE and the Venezuelan Ministry of Energy and Mines conducted cooperative research on MEOR; a final report titled “Microbial Enhanced Oil Recovery” was published in April, 1997 (DOE/BC-97/3/SP OSTI ID:14278). This report contains research results and documentation/references in the field of MEOR. The report cites many of the spin-off technologies from MEOR, including waste remediation and refining (upgrading of crude oil). MEOR processes continue to be evaluated for the following applications:
- Microbial Well Stimulation. This process is being applied on a commercial basis throughout the world. The major applications have been in the heavier oil reservoirs dealing with problems associated with paraffin and asphaltene deposits. The major areas of application include the United States, Venezuela, China, and Indonesia.
- Microbial Enhanced Waterflooding. This process, which requires the transport of nutrients over a long distance within the reservoir, is still in the development phase. DOE has field-tested this process in several fields in Oklahoma.
- Profile Control and Sweep Improvement. This process uses microbes that produce polymers, biomass, and slimes that selectively plug the more permeable zones. This process is still in the development phase. DOE has field-tested this process in an oil field in Alabama.
MEOR has two distinct advantages: 1) microbes do not consume large amounts of energy, and 2) the use of microbes is not dependent on the price of crude oil, as compared with other EOR processes. In some reservoirs, beneficial microbes are indigenous and only need nutrients to stimulate growth. Because microbial growth occurs at exponential rates, it should be possible to produce large amounts of useful products rapidly from inexpensive and/or renewable resources. Thus, MEOR has the potential to be more cost-effective than other EOR processes. Studies have shown that several microbially produced biosurfactants compare very favorably with chemically synthesized surfactants. The ability to produce effective surfactants at a low price may make it possible to recover substantial amounts of residual oil.
In one NETL MEOR project, microbes native to the Eutaw Formation located in Wayne County, MS, are being used to produce polymers that will help redirect the flow of fluids in the oil reservoir and to improve the sweep efficiency of a carbon dioxide gas flood in Eucatta field. To encourage the microbes to produce the polymer, a batch of nutrients is injected into the oil reservoir. The CO2 follows the injection of the nutrient compound and is expected to capture more of the original-oil-in-place, thus improving overall oil production from the field.
NETL research also is being conducted to generate surfactants from native bacteria at the surface for injection into the oil reservoir. The biosurfactant reduces the interfacial tension of the fluids in the reservoir and allows more oil to be produced. Mutant strains of the bacteria are selected based on their ability to produce biosurfactants and then cloned to transform the population of the microbes. The main advantage to this method is that no external nutrient source is required.
Another means of using microbes in the oil industry involves the use of bacteria to prevent sulfide production. Sulfides are a serious problem caused by sulfate-reducing bacteria in the reservoir. The sulfides can plug wells, reducing oil production; they also can generate hydrogen sulfide, a deadly gas. In another NETL MEOR project, a special nutrient is injected into the reservoir for nitrate-based bacteria. Over time, the nitrate-based bacteria overtake the sulfate-reducing bacteria and eventually eliminate the production of sulfides.
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| This photograph shows researchers sampling a wellhead to conduct fluid analysis and microbial ecology and physiological characterization tests, work that is featured in the fact sheet entitled Microbial Enhanced Oil Recovery Surfactant from Waste Products and Biotechnologies for Oil Field Application, Project No. FEW 5AC312.
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