Porewater Geochemical Assessment of Seismic Indications for Gas Hydrate Presence and Absence: Mahia Slope, East of New Zealand’s North Island

Richard B. Coffin, Gareth Crutchley, Ingo Pecher, Brandon Yoza, Thomas J. Boyd and Joshu Mountjoy
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Richard B. Coffin: Department of Physical and Environmental Science, Texas A&M University—Corpus Christi, Corpus Christi, TX 78412, USA
Gareth Crutchley: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24103 Kiel, Germany
Ingo Pecher: Department of Physical and Environmental Science, Texas A&M University—Corpus Christi, Corpus Christi, TX 78412, USA
Brandon Yoza: Hawai’i Natural Energy Institute, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
Thomas J. Boyd: US Naval Research Laboratory, Code 6181, 4555 Overlook Ave., SW, Washington, DC 20001, USA
Joshu Mountjoy: National Institute of Water and Atmosphere, Wellington 5012, New Zealand

Energies, 2022, vol. 15, issue 3, 1-18

Abstract: We compare sediment vertical methane flux off the Mahia Peninsula, on the Hikurangi Margin, east of New Zealand’s North Island, with a combination of geochemical, multichannel seismic and sub-bottom profiler data. Stable carbon isotope data provided an overview of methane contributions to shallow sediment carbon pools. Methane varied considerably in concentration and vertical flux across stations in close proximities. At two Mahia transects, methane profiles correlated well with integrated seismic and TOPAS data for predicting vertical methane migration rates from deep to shallow sediment. However, at our “control site”, where no seismic blanking or indications of vertical gas migration were observed, geochemical data were similar to the two Mahia transect lines. This apparent mismatch between seismic and geochemistry data suggests a potential to underestimate gas hydrate volumes based on standard seismic data interpretations. To accurately assess global gas hydrate deposits, multiple approaches for initial assessment, e.g., seismic data interpretation, heatflow profiling and controlled-source electromagnetics, should be compared to geochemical sediment and porewater profiles. A more thorough data matrix will provide better accuracy in gas hydrate volume for modeling climate change and potential available energy content.

Keywords: seismic data; sub-bottom profiler data; methane; vertical migration; carbon isotope analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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