Distinct expressions of the BSR using various frequencies offshore Uruguay and its correspondence with the gas hydrate stability zone.

Tomasini, Juan, Preu, Benedict, Krastel, Sebastian, Schwenk, Tilmann, Spiess, Volkhard and de Santa Ana, Héctor (2011) Distinct expressions of the BSR using various frequencies offshore Uruguay and its correspondence with the gas hydrate stability zone. [Talk] In: 7th International Conference on Gas Hydrates (ICGH 2011). , 17.-21.07.2011, Edinburgh, Scotland, United Kingdom .

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Abstract

At the Uruguayan continental margin, seismic evidence for the occurrence of gas hydrate has been identified based on the presence of BSRs in densely spaced 2D reflection seismic sections from different surveys. Mapping of BSRs based on 2D seismic data acquired in 2007 and 2008 suggested the presence of gas hydrates in areas that were not previously identified; hence hydrate occurrence offshore Uruguay is more widespread than previously thought. Recently ANCAP has digitized offshore seismic data acquired between 1970 and 1982. Being able to work on this data using interpretation software, and integrating results with the latest interpretations performed on the seismic collected in 2007 and 2008, the BSR extends over an area of approximately 25.000 km2. It is present in water depths greater than 500 m and has high continuity in Pelotas Basin but is more discontinuous at Punta del Este Basin and southern part of Oriental del Plata Basin.
In offshore basins around the world the base of GHSZ can have different seismic expressions such as continuous, segmented, and high-relief BSRs depending on the stratigraphic, fluid and geothermal setting. Here, we present examples of the influence of the acquisition parameters on the acoustic expression of the BSR, comparing commercial seismic sections acquired for hydrocarbon exploration and high resolution seismic sections acquired during the R/V Meteor Cruise M49/2 in 2001 and R/V Meteor Cruise M78/3a (May - June 2009) using different sources and streamer system. For the different data sets the BSR presents differences regarding its continuity and amplitude strength. In high resolution seismic, enhanced amplitudes and phase reversals are observed for several reflectors while deep penetration seismic shows only one single continuous reflector.
This comparison may help to visualize the complexity of the free gas, gas hydrate and stratigraphic system behind the BSR, which is usually masked on low-frequency deep penetration seismic data.

Document Type: Conference or Workshop Item (Talk)
Keywords: Seismology; Gas hydrates, offshore Uruguay, seismic imaging
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-JRG-B4 Submarine Hazards
Date Deposited: 05 Dec 2011 11:12
Last Modified: 06 Jul 2012 14:50
URI: http://oceanrep.geomar.de/id/eprint/12700

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