Summary Using a breakthrough process, which does not require microbes to be injected, more than 100 microbial enhanced-oil-recovery (MEOR) treatments were conducted from 2007 to the end of 2010 in oil-producing and water-injection wells in the United States and Canada. On average, these treatments increased oil production by 122%, with an 89% success rate. This paper reviews the MEOR process, reviews the results of the first 100+ treatments, and shares what has been learned from this work. Observations and conclusions include the following: Screening reservoirs is critical to success. Identifying reservoirs where appropriate microbes are present and oil is movable is the key. MEOR can be applied to a wide range of oil gravities. MEOR has been applied successfully to reservoirs with oil gravity as high as 41° API and as low as 16° API. When microbial growth is appropriately controlled, reservoir plugging or formation damage is no longer a risk. Microbes reside in extreme conditions and can be manipulated to perform valuable in-situ "work." MEOR has been applied successfully at reservoir temperatures as high as 200°F and salinities as high as 140,000 ppm total dissolved solids (TDS). MEOR can be applied successfully in dual-porosity reservoirs. A side benefit of applying MEOR is that it can reduce reservoir souring. An oil response is not always observed when treating producing wells. MEOR can be applied to many more reservoirs than thought originallys with little downside risk. This review of more than 100 MEOR well treatments expands the types of reservoirs in which MEOR can be applied successfully. Low-risk and economically attractive treatments can be accomplished when appropriate scientific analysis and laboratory screening are performed before treatments.

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Using a breakthrough process, which does not require microbes to be injected, over one hundred Microbial Enhanced Oil Recovery (MEOR) applications have been conducted since 2007 in producing oil and water injection wells in the United States and Canada. On average, these applications increased oil production by 127% with an 89% success rate. This paper reviews the MEOR process, reviews the results of the first one hundred plus applications and shares what has been learned from this work. Observations and conclusions include the following: Screening reservoirs is critical to success. Identifying reservoirs where appropriate microbes are present and oil is movable is the key.MEOR can be applied to a wide range of oil gravities. MEOR has been successfully applied to reservoirs with oil gravity as high as 41° and as low as 16° API.When bacteria growth is appropriately controlled, reservoir plugging or formation damage is no longer a risk.Microbes reside in extreme conditions and can be manipulated to perform valuable in-situ "work." MEOR has been applied successfully at reservoir temperatures as high as 200°F and salinities as high as 140,000 ppm TDS.MEOR can be successfully applied in dual-porosity reservoirs.A side benefit of applying MEOR is that it can reduce reservoir souring.An oil response is not always seen when treating producing wells. The application of MEOR can be applied to many more reservoirs than originally thought with little downside risk. This review of more than a hundred MEOR applications expands the types of reservoirs where MEOR can be successfully applied. Low risk and economically attractive treatments can be accomplished when appropriate scientific analysis and laboratory screening is performed prior to treatments.

A Microbial Enhanced Oil Recovery (MEOR) application in the Big Wells Field located in Dimmit County, Texas has shown a significant improvement in production—both oil rate and water cut performance. As a result of a specific nutrient injection designed in the laboratory to stimulate in situ, naturally occurring microbes, for this San Miguel sandstone reservoir and its microbial ecology, a marked improvement was seen in the two producing wells to which the treatment was applied. The water cut in one well improved from fifty per cent to fifteen percent. The water cut in a second well improved from fifty-five to thirty-five percent. Although previous field applications of this MEOR process had shown increases in oil production and decreases in water production, water production in this application was completely stopped for a brief time as a result of the treatment. This paper reviews the Big Wells producing well treatments and their results. A specific look at the oil release mechanism of this MEOR process offers an explanation as to how the oil released by these treatments impacts the relative permeability of fluids in the reservoir near the treated wellbores as demonstrated in the field producing well treatments. Similar benefits are seen during the treatment of water injection wells related to performance in adjacent producing wells. The significance of this application is that field evidence supports that production improvements result from the release of oil in sufficient quantities to change the near wellbore relative permeability to both oil and water. Also, it demonstrates that this MEOR technology can be successfully applied to reservoirs in this geographical area and extends the lower threshold for formation permeability suitable for treatment. Having been successfully applied in other parts of North America, this is an important application of this MEOR technology in Texas.