An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru

American Association of Petroleum Geologists Bulletin
By: , and 

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Abstract

Seismic reflection data recorded near ODP Site 688, offshore Peru, exhibit a persistent bottom-simulating reflector (BSR) from a depth corresponding to the theoretical base of the gas hydrate stability field. Although gas hydrate has been recovered in cores from scientific drilling in both the Pacific and the Atlantic, drilling in areas exhibiting a BSR has usually been avoided because of the perceived risk of releasing free gas trapped beneath the hydrated sediments. To carry out a quantitative analysis of the BSR, the seismic data were reprocessed using signature deconvolution and true amplitude recovery techniques. Synthetic seismograms that were created using acoustic parameters extracted from the seismic data and physical properties from Site 688 borehole measurement were compared to the observed seismic data to estimate the thickness of the free-gas zone. Results indicate the BSR is discontinuous laterally. Where the BSR is of high amplitude, free gas in a zone 5.5-17 m thick beneath the hydrated sediments provides the observed waveform; where the BSR amplitude is low, the free-gas zone is much thinner than 5.5 m or is entirely absent.

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Publication type Article
Publication Subtype Journal Article
Title An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru
Series title American Association of Petroleum Geologists Bulletin
DOI 10.1306/0C9B288F-1710-11D7-8645000102C1865D
Volume 75
Issue 5
Year Published 1991
Language English
Publisher American Association of Petroleum Geologists
Description 15 p.
First page 910
Last page 924
Country Peru
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