Methane recycling between hydrate and critically pressured stratigraphic traps, offshore Mauritania

Abstract

Research Article| November 01, 2010 Methane recycling between hydrate and critically pressured stratigraphic traps, offshore Mauritania Richard J. Davies; Richard J. Davies Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, University of Durham, Science Labs, Durham DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Amy L. Clarke Amy L. Clarke Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, University of Durham, Science Labs, Durham DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Richard J. Davies Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, University of Durham, Science Labs, Durham DH1 3LE, UK Amy L. Clarke Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, University of Durham, Science Labs, Durham DH1 3LE, UK Publisher: Geological Society of America Received: 25 Jan 2010 Revision Received: 30 May 2010 Accepted: 06 Jun 2010 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2010 Geological Society of America Geology (2010) 38 (11): 963–966. https://doi.org/10.1130/G31058.1 Article history Received: 25 Jan 2010 Revision Received: 30 May 2010 Accepted: 06 Jun 2010 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Richard J. Davies, Amy L. Clarke; Methane recycling between hydrate and critically pressured stratigraphic traps, offshore Mauritania. Geology 2010;; 38 (11): 963–966. doi: https://doi.org/10.1130/G31058.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Three-dimensional seismic reflection data from offshore Mauritania reveal a base hydrate reflection, beneath which are 56 stratigraphically trapped gas accumulations (∼0.08 Gt methane). Only 2 are sealed by the base of the hydrate (∼0.004 Gt methane) and therefore constitute the free gas zone. Some of the stratigraphically trapped gas accumulations are critically pressured. There are also 360 gas chimneys beneath the gas hydrate, but not outside the region covered by it. They are evidence for repetitious leaking from the accumulations. Only 12 of the chimneys terminate at a contemporaneous seabed, showing that methane venting was not significant. Instead, upward resetting of the base hydrate triggered gas dissociation and caused the traps to become charged and critically pressured. Vertical leaking to intermediate, shallower stratigraphic traps or to the gas hydrate itself, where it was reincorporated, occurred once the seal capacity was exceeded. Most (95%) of the free gas is stored stratigraphically and re-migrates in this way, and this trapping mechanism may be typical of fine-grained passive margin continental slopes. Only 5% of the gas is within the free gas zone. The role of recycling of methane between the hydrate and stratigraphic traps has not previously been recognized and represents a store for this greenhouse gas that is not susceptible to changes in ambient conditions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.