Microbial DNA tracks subsurface fluid pathways

DNA ‘barcode’ overcomes limited ‘traditional methods’ for identifying well connections and natural fractures.

Researchers at MIT have discovered* a novel way of fingerprinting underwater by sequencing the DNA of microbial communities in samples of reservoir fluids. The approach is used to identify fluid pathways through the subsurface. Lara Streiff, writing in Stanford Earth Matters explained that ‘traditional methods for identifying well connections and natural fractures, well logging and borehole imaging, have significant limitations [.. as .. ] they do not reach the large spaces between wells. Seismic data can describe a larger area, but with limited resolution’. Analyzing the chemistry of these fluids is also useful, but the DNA of the microbial community is said to produce more specific results.

The Stanford study targeted geothermal wells where water is circulated through the subsurface to recover thermal energy. As water travels through the subsurface it picks-up a unique collection of microbes that create a revealing DNA ‘barcode’. Mapping actual trajectories between injectors and producers has been facilitated by the approach which also has application in oil extraction and carbon sequestration. The technique has application in mapping the spread of contamination, assessing artificial fracturing effects or determining the leakage potential of a carbon sequestration site. The method was tested at the Stanford underground research facility in Lead, South Dakota, once the deepest gold mine in North America. The study, authored by Yuran Zhang was published in the November 2019 issue of Water Resources Research. The research was supported by the Stanford TomKat Center for sustainable energy.

* There is already quite a body of knowledge on microbial DNA in the oilfield. A search on OnePetro produces 33 references to ‘microbial DNA’.

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