Optimization of microbial control in the oilfield using molecular methods

Microorganisms present multiple challenges in oilfield systems such as microbiologically influenced corrosion (MIC), reservoir souring, and biofouling.  The selection of chemistries to minimize microbial risk has traditionally relied on culture-based methods such as serial dilution to determine biocide efficacy.  However, the diversity of microbes and the unique conditions found in each oil and gas asset make it very challenging to obtain reliable results through growth assays in the culture media commonly used.

Biocide selection has evolved significantly in the past 5-10 years to include more advanced methodologies such as the quantification of ATP.  These ATP methods are now commonly used in the field and are ever evolving to reduce the interferences caused by oilfield fluids and to look at other parameters such as dormancy through the examination of AMP.

Our research has shown that a single method for performance evaluation does not always provide the definitive information required to select a biocide for field usage.  Instead, we are using a multifaceted approach which includs the use of qPCR, Flow Cytometry, Next-Generation DNA sequencing, and Third-Generation ATP and AMP quantification to determine an optimal treatment strategy.  

Incorrect selection of biocides can lead to significant issues in field operation, including resistance and/or lack of susceptibility by the microbial population to biocide treatment.  An example of the power achieved from combining molecular methods is described here for a complex biocide recommendation for a production system for the Eagle Ford Shale, located in South Texas.  Our evaluation methods identified a combination of chemistries to reduce plugging from suspended solids and mitigate the risk of corrosion failures.