Microbial Enhanced Oil Recovery (MEOR)

                                    

    Introduction

    After traditional oil recovery processes, large amount of residual oil are still trapped in the pore spaces of the complex capillary network of the reservoir.Microbial Enhanced Oil Recovery (MEOR) is a tertiary oil recovery technique that utilizes microorganisms and their metabolic products to increase the extraction of crude oil from reservoirs. This method leverages the natural capabilities of microbes to alter the physical and chemical properties of oil and the reservoir environment to enhance oil recovery.

    Types of MEOR

    1. In Situ MEOR:

    Microorganisms are injected directly into the oil reservoir along with nutrients that stimulate their growth and activity. The microbes produce substances such as biosurfactants, biopolymers, acids, solvents, and gases within the reservoir, which help mobilize and displace oil.

    2. Ex Situ MEOR:

    Microbial metabolites (e.g., biosurfactants, gases) are produced outside the reservoir in bioreactors and then injected into the oil reservoir. This approach is used when it is challenging to control microbial activity directly within the reservoir.

    Process of MEOR

    1. Selection of Microorganisms:

    Microorganisms are chosen based on their ability to produce beneficial metabolites under reservoir conditions. Commonly used microbes include bacteria, archaea, and fungi.

    2. Injection of Microorganisms and Nutrients:

    In in situ MEOR, selected microbes and nutrients (e.g., carbon sources, nitrogen, phosphorus) are injected into the reservoir through injection wells.

    3. Microbial Growth and Metabolism:

    The microbes grow and metabolize the nutrients, producing substances such as biosurfactants, biopolymers, gases (CO2, CH4), solvents (ethanol, acetone), and acids (lactic acid).

    4. Oil Mobilization and Displacement:

    The microbial products reduce oil viscosity, alter wettability, increase reservoir pressure, and create microchannels in the rock matrix, facilitating the flow of oil towards production wells.

    5. Production:

       Mobilized oil is extracted through production wells.

    Different Types of Microbes Used in MEOR

    1. Bacteria:

       - Bacillus spp.: Produce biosurfactants and biopolymers.

       - Pseudomonas spp.: Known for biosurfactant production.

       - Clostridium spp.: Generate solvents and gases through fermentation.

    2. Archaea:

       - Methanogens (e.g., Methanococcus spp.): Produce methane from organic substrates.

    3. Fungi:

       - Aspergillus spp.: Capable of degrading heavy hydrocarbons.

    Advantages of MEOR

    1. Cost-Effective:

     MEOR is generally less expensive compared to thermal and chemical EOR methods.

    2. Environmental Friendliness:

     Utilizes natural biological processes, reducing the need for harsh chemicals and high-energy inputs.

    3. Enhanced Oil Recovery:

    Can recover additional oil that is inaccessible by primary and secondary methods, increasing the overall recovery factor.

    4. Reservoir Conditioning:

     Microbial activities can improve the overall health and longevity of the reservoir.

    Challenges of MEOR

    1. Reservoir Conditions:

    High temperatures, salinity, and pressure can inhibit microbial activity and metabolite production. Engineering resilient microbial strains is necessary.

    2. Nutrient Delivery:

    Ensuring effective and uniform distribution of nutrients throughout the reservoir without causing blockages or unwanted microbial growth is challenging.

    3. Microbial Control:

    Controlling microbial growth to prevent souring (H2S production) and other negative effects is critical.

    4. Compatibility:

     Compatibility of microbial metabolites with reservoir rocks and fluids must be ensured to prevent clogging and other issues.

    5. Economic Viability:

     Comprehensive economic assessments are required to justify the initial investment and operational costs.

    Conclusion

    Microbial Enhanced Oil Recovery is a promising and evolving technology in the oil industry. By leveraging the natural capabilities of microorganisms, MEOR offers a cost-effective and environmentally friendly alternative to traditional oil recovery methods. Continued research and technological advancements are essential to overcome the challenges and optimize the application of MEOR in diverse reservoir conditions.

    References