Microbial technology applications in wellbore stimulation and oil recovery enhancement: A review

The different microbial technologies to enhance oil recovery have not yet been proven for two main reasons. Firstly, most microbial enhanced oil recovery (MEOR) field trials lack structured research methodology. Secondly, it is difficult to interpret MEOR tests. In order to correlate qualitatively the effects on oil recovery with the nutrient injections, other variables should be kept constant for a long time which is hard. Correlating these quantitatively is far more difficult. Another challenge is to decide accurately on the mechanisms through which microbes are affecting the oil recovery. To achieve this, additional wells have to be drilled, brine and oil chemical analysis have to be performed and DNA analysis have to be conducted. So far, it is believed that field trials intended to increase volumetric efficiency have yielded mixed results, whereas those designed to reduce permeability through biomass production of microbes are simpler and have a higher chance of success.