DNA Barcoding for Fractured Reservoir Analysis – An Initial Investigation

Tracer testing in fractured reservoirs has long been limited by the availability of unique and unambiguous tracers. In this study, we introduce the concept of using thermophilic microorganisms and DNA barcoding techniques for fractured reservoir characterization. On the one hand, thermophilic microorganisms have the potential of thriving in the extreme environment of geothermal and oil reservoirs. On the other hand, even if the microbes lose the basic functions of life after passing through the subsurface, their genetic information may still be retrieved and identified using modern sequencing technologies. In addition, because microorganisms are able to replicate themselves given appropriate nutrients and growing conditions, they are also a cost-effective solution for potential up-scaled field tracer testing applications. Heating experiments were conducted to examine the possibility of short-fragment identification of archaeal genomic DNA after prolonged heat treatment. The results show that it is feasible to still identify a short region of genomic DNA even after prolonged heat treatment, and a short region within a long genomic DNA appears to be more robust than a similar-length shortstranded DNA. We therefore conclude that the concept of using thermophilic microorganisms combined with DNA barcoding techniques to perform unambiguous reservoir tracer analysis shows good promise. To avoid confusion with the indigenous microbes in a reservoir, either exogenous microbes or engineered microbes containing artificial barcodes may be used.