Gas venting that bypasses the feather edge of marine hydrate,offshore Mauritania |
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| Institution: | 1. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China;2. Gas Hydrate Geology Division, Qingdao Institute of Marine Geology, Qingdao, 266071, China;3. School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, Tyne and Wear, NE1 7RU, UK;4. Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, Science Labs, Durham University, DH1 3LE, UK;5. Research Institute of Unconventional Petroleum and New Energy, China University of Petroleum, Qingdao, Shandong, 266580, China;1. GNS Science, Institute for Geological and Nuclear Sciences, PO Box 30368, Lower Hutt 5040, New Zealand;2. School of Environment, The University of Auckland, Private Bag 92019, Auckland, New Zealand;1. Earth Sciences Department, University of Oxford, South Parks Road, Oxford, OX1 3 AN, UK;2. SpectrumGeo Ltd. Dukes Court, Duke Street, Woking, Surrey, GU21 5BH, UK;1. School of Earth Sciences, The Ohio State University, 125 South Oval Mall, Columbus, OH 43210, USA;2. Dokuz Eylül University, Institute of Marine Sciences and Technology, Haydar Aliyev Blv., 35340 Inciralti, Izmir, Turkey;3. Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, USA;1. Università Degli Studi di Roma Tre, Dipartimento di Scienze, Sezione di Scienze Geologiche, Largo San Leonardo Murialdo 1, 00146 Roma, Italy;2. Sapienza Università di Roma, Dipartimento di Scienze Della Terra, Piazzale Aldo Moro 5, 00185 Roma, Italy;3. INGV, Via di Vigna Murata 605, 00100 Roma, Italy;4. Università Degli Studi di Perugia, Dipartimento di Fisica e Geologia, Via Alessandro Pascoli, 06123 Perugia, Italy;5. Eni SpA e Exploration & Production Division, Via Emilia, San Donato Milanese, 20097 Milano, Italy;6. Instituto de Ciências da Terra (Pólo da FCUP) e Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal;1. GEOMAR Helmholtz Centre for Ocean Research, Wischhofstr. 1-3, 24148, Kiel, Germany;2. ExxonMobil Upstream Research, 22777 Springwoods Village Parkway, Spring, TX, 77389, USA;3. Dokuz Eylül University, Institute of Marine Sciences and Technology, Haydar Aliyev Boulevard 100, 35340, Turkey;4. Laboratoire Aléas géologiques et Dynamique sédimentaire, Centre Bretagne - ZI de la Pointe du Diable, CS 10070, 29280 Plouzané, France;1. Dipartimento di Scienze della Terra, Università degli Studi di Pisa, Via S. Maria 53, 56126 Pisa, Italy;2. Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, 50121 Firenze, Italy;3. Geology and Petroleum Geology Department, University of Aberdeen, King''s College, Aberdeen AB24 3DS, United Kingdom;4. Consiglio Nazionale delle Ricerche, IGG, UOS Firenze, Via G. La Pira 4, 50121 Firenze, Italy |
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| Abstract: | Methane can be released from the vast marine hydrate reservoirs that surround continents into oceans and perhaps the atmosphere. But how these pathways work within the global carbon cycle now and during a warmer world is only partially understood. Here we use 3-D seismic data to identify what we interpret to be a gas venting system that bypasses the hydrate stability zone (HSZ) offshore of Mauritania. This venting is manifested by the presence of the acoustic wipe-out (AWO) across a densely faulted succession above a salt diapir and a set of morphological features including a substantial, ～260 m wide and ～32 m deep, pockmark at the seabed. The base of the HSZ is marked by a bottom simulating reflector (BSR) which deflects upwards above the diapir, rather than mimicking the seabed. We use a numerical modelling to show that this deflection is caused by the underlying salt diapir. It creates a trapping geometry for gas sealed by hydrate-clogged sediment. After entering the HSZ, some methane accumulated as hydrate in the levees of a buried canyon. Venting in this locality probably reduces the flux of gas to the landward limit of feather edge of hydrate, reducing the volume of gas that would be susceptible for release during a warmer world. |
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| Keywords: | Gas hydrate BSR Gas venting Diapir |
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