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High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

Author

Listed:
  • Iván Vargas-Cordero

    (Facultad de Ingeniería, Universidad Andres Bello (UNAB), 2531015 Viña del Mar, Chile)

  • Umberta Tinivella

    (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), 34010 Trieste, Italy)

  • Lucía Villar-Muñoz

    (Helmholtz Centre for Ocean Research (GEOMAR), 24148 Kiel, Germany)

  • Joaquim P. Bento

    (Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, 2360007 Valparaíso, Chile)

Abstract

Recent studies have reported cold seeps offshore of Mocha Island. Gas hydrate occurrences along the Chilean margin could explain seeps presence. Gas-phase (gas hydrate and free gas) and geothermal gradients were estimated analysing two seismic sections. Close to Mocha Island (up to 20 km) were detected high (up to 1900 m/s) and low (1260 m/s) velocities associated with high gas hydrate (up to 20% of total volume) and free gas (up to 1.1% of total volume) concentrations, respectively. A variable and high geothermal gradient (65–110 °C/km) was obtained. These results are related to high supply of deep fluids canalised by faults and fractures. Faraway from Mocha Island (>60 km), free gas concentrations decrease to 0.3% of total volume and low geothermal gradient (from 35 to 60 °C/km) are associated with low fluids supply. Finally, we propose gas hydrate dissociation processes as the main supply source for seeps in the vicinity of Mocha Island. These processes can be caused by: (a) active faults and seismic activity; and (b) warm fluid expulsion from deeper zones altering hydrate stability conditions. In both cases, gas hydrate dissociation could generate slope instability and landslides, as occurred in the past in this region and reported in the literature.

Suggested Citation

  • Iván Vargas-Cordero & Umberta Tinivella & Lucía Villar-Muñoz & Joaquim P. Bento, 2018. "High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island," Energies, MDPI, vol. 11(11), pages 1-13, November.
    • Handle: RePEc:gam:jeners:v:11:y:2018:i:11:p:3062-:d:181179
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    References listed on IDEAS

    as
    1. Wei-Li Hong & Marta E. Torres & JoLynn Carroll & Antoine Crémière & Giuliana Panieri & Haoyi Yao & Pavel Serov, 2017. "Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming," Nature Communications, Nature, vol. 8(1), pages 1-14, August.
    2. Vargas-Cordero Iván & Tinivella Umberta & Villar-Muñoz Lucía, 2017. "Gas Hydrate and Free Gas Concentrations in Two Sites inside the Chilean Margin (Itata and Valdivia Offshores)," Energies, MDPI, vol. 10(12), pages 1-11, December.
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    Cited by:

    1. Ivan Vargas-Cordero & Michela Giustiniani & Umberta Tinivella & Lucia Villar-Muñoz & Giulia Alessandrini, 2021. "Gas Hydrate System Offshore Chile," Energies, MDPI, vol. 14(3), pages 1-13, January.
    2. Sha Song & Umberta Tinivella & Michela Giustiniani & Sunny Singhroha & Stefan Bünz & Giorgio Cassiani, 2018. "OBS Data Analysis to Quantify Gas Hydrate and Free Gas in the South Shetland Margin (Antarctica)," Energies, MDPI, vol. 11(12), pages 1-16, November.

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