Overpressure of a deep ocean natural gas reservoir led to a massive methane release that could have reached the atmosphere early in the Pliocene, according to a study. While methane seeps from shallow seas may contribute to global atmospheric methane concentrations, releases from deep oceans are generally absorbed by the water column and do not typically reach the atmosphere. Martino Foschi and colleagues used 3D seismic data, borehole information, and fluid flow modeling to estimate the amount of methane released during the Pliocene from a reservoir in the Atlantic Ocean's Faroe-Shetland Basin. The authors noted eight kilometer-scale pockmarks in the ancient seabed above the reservoir and the seepage zone, indicating a sudden fluid expulsion. The authors estimate that up to 27 teragrams of methane, representing 62% of the methane stored in the reservoir, could have reached the atmosphere over the course of less than 8 months. The authors note that this reservoir-sized gas emission is equivalent to 10% of current global annual natural methane emissions or 28% of emissions produced by the oil and gas industry. According to the authors, the geologic conditions that led to this ultraseepage currently exist in many regions.
ARTICLE #20-01904: "Evidence for massive emission of methane from a deep-water gas field during the Pliocene," by Martino Foschi, Joseph A. Cartwright, Christopher W. MacMinn, and Giuseppe Etiope.
MEDIA CONTACT: Martino Foschi, University of Oxford, UNITED KINGDOM; e-mail: martino.foschi@earth.ox.ac.uk
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Proceedings of the National Academy of Sciences