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Lecture 11. Microbial Enhanced Oil Recovery

I. Assigned References

A. McInerney and Sublette, Petroleum Microbiology: Biofouling, Scouring, and Improved Oil Recovery, pp. 600-607, Hurst et. al., eds., Manual of Environmental Microbiology, ASM Press, Washington, D. C., 1997.

B. Banat, I. M., Biosurfactants production and possible uses in microbial enhanced oil recovery and oil pollution remediation: a review. Bioresource Technology, 51, 1-12, 1995.

II. Enhanced Oil Recovery (EOR)

A. Tertiary or Third Phase

B. Other Phases

1. primary: use of natural stored energy or pumping
2. secondary: injection of water to force oil recovery
3. recovery less than 40% of oil reserves

C. Mechanisms

1. surfactant polymer flooding: reduction in interfacial tension and increased water viscosity
2. solvent flooding: swelling is preferred over solution
3. emulsification: oil swelling; viscosity reduction
4. gas-oil-water: swelling; carbon dioxide used
5. steam flooding: viscosity reduction; steam distillation
6. in situ combustion: burning front; generates gases, steam, hot water

III. Mechanisms of Microbial Enhanced Oil Recovery (MEOR)

A. Proposed Mechanisms

1. In situ generation of CO₂ for pressure and solubilization
2. microbial production of organic acids
3. conversion of hydrocarbons to lower molecular weight
4. production of surface active agents
5. encouragement of consolidation of oil to droplets
6. enzymatic modification of hydrocarbons
7. viscosity improvement

B. Contribution of Microbial Products

C. Types of Microbial Processes for MEOR

D. Overall Mechanisms of Stimulation of Oil Production

E. Wellbore Cleaning

1. Acids:

The acids react with various minerals, especially carbonates, and loosen clay particles and other inorganic deposits.

2. Solvents:

Solvents dissolve or swell the precipitated organic deposits, improving the mobility of the oil phase.

3. Biogas:

After a shut-in period of about 1 to 4 weeks for anaerobic growth, the pressure around the well bore was raised to 200-300 psi. When the well was opened and allowed to blow out, a considerable amount of sludge and drilling mud were removed. The well was then placed back in production.

IV. Examples of MEOR Process Concepts

A. Displacement of Oil by Metabolites of Inoculated Bacteria Grown In Situ

B. Selective Plugging of Highly Permeable Zones by Bacteria

C. Huff and Puff

1. huff: Migration of cells and synthesis of metabolic products following inoculation and closing of injection well
2. puff: production and recovery of oil after incubation period

V. Environmental Issues

A. Subsurface water

1. migration of organisms or metabolites into groundwater

B. Wastewater

1. spent fluids due to additional drilling
2. equipment washing
3. brinewater, media, chemicals for pH adjustment

C. Atmospheric Emissions (e.g. H₂S)

D. Solid Wastes

1. bacteria in filter solids

VI. Status of MEOR

D. Poland, 1961-71

1. used bacteria and molasses
2. gases were produced, mainly methane
3. oil viscosity decreased from 9 to 3 cp
4. oil production increased from 20 - 200% for 9 mo to 8 years

E. Romania

1. seven field trials with molasses enrichments
2. two worked with 200% increases for 1-5 years

VII. Research and Development Needs

A. Laboratory Screening of Organisms

B. Field Tests of Organisms

C. Effects of MEOR on Viscosity

D. Bacterial Transport Through Porous Media

E. Production of Surfactants

1. table of biosurfactants produced by bacteria
2. effects of surfactant solutions releasing crude oil from sand

F. Multidisciplinary

1. geology
2. chemistry
3. microbiology
4. fluid mechanics
5. petroleum engineering
6. environmental engineering
7. chemical engineering