Changing needs and treatment strategies for microbial control in oil and gas applications

Microbiological contamination in oil and gas applications has been recognized as a cause of souring (sulfide), corrosion (organic acids), and plugging (biofilms, FeS₂precipitates).  These problems can impact the quality of the petroleum resource and damage structural assets. Industrial biocides have been used for decades to control microbial growth.  In the past, biocides were typically selected by doing short term (1-2 hr) kill tests at room temperature with single actives.  With the growing focus on downhole reservoir integrity for both hydraulic fracturing and water flooding, there is an increasing demand for biocides that can provide longer term effectiveness under more severe environmental conditions, including elevated temperature, pH and salinity.  In addition, new types of problem-causing anaerobic microorganisms have been identified and improved methods are able to monitor microbial populations beyond classic bug bottle testing.  These methods include molecular (genetic) testing, advanced microscopy, and rapid metabolic assays.  In order to identify optimum microbial treatment technologies to meet these industry challenges, novel biocide efficacy testing methods and new biocide combinations have been implemented in the field.  This paper will provide a review of the evolution of microbial monitoring methods, biocide technologies, and treatment strategies that have been developed over time.