Detection of free gas and gas hydrate based on 3D seismic data and cone penetration testing: An example from the Nigerian Continental Slope

Type Article
Date 2007-06
Language English
Author(s) Sultan NabilORCID1, Voisset Michel1, Marsset TaniaORCID1, Vernant Antoine-Mathieu1, Cauquil E2, Colliat J2, Curinier V2
Affiliation(s) 1 : IFREMER, Dept Geosci Marines, F-29280 Plouzane, France.
Source Marine Geology (0025-3227) (Elsevier), 2007-06 , Vol. 240 , N. 1-4 , P. 235-255
DOI 10.1016/j.margeo.2007.02.012
WOS© Times Cited 37
Keyword(s) Piezocone, Niger delta, Gas hydrate, Free gas, Effective medium theory
Abstract We present a new method to characterize free gas, gas hydrates and carbonate concretions occurrence which are considered as high-risk factors for sub-sea developments in the Niger delta. This method is based on the combination of 3D seismic data to the geotechnical site characterizations using piezocone CPTU tests (Cone Penetration Test with additional measurement of the pore water pressure). A special processing of the 3D seismic data has enabled the determination of the interval compressional velocity. Using the effective-medium theory, velocity anomalies (negative and positive) within the first 15 m were translated in gas hydrate and free gas distribution. The calibration of the P wave velocity anomalies was done thanks to in-situ geotechnical testing carried out during two oceanographic surveys (2003 and 2004). Comparison between in-situ testing, recovered cores and the prediction of the gas and the gas hydrate distribution based on the compressional wave velocity have shown that 3D seismic data is a valuable tool to identify heterogeneous areas but the use of the piezoeone was essential to discriminate between gas hydrate occurrences and carbonate concretions' presence. Furthermore, in-situ compressional wave velocity (V-p) measurements have clearly demonstrated what it was suspected from the 3D seismic data, the co-existence in the study area between gas hydrate and free gas. (c) 2007 Elsevier B.V. All rights reserved.
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Sultan Nabil, Voisset Michel, Marsset Tania, Vernant Antoine-Mathieu, Cauquil E, Colliat J, Curinier V (2007). Detection of free gas and gas hydrate based on 3D seismic data and cone penetration testing: An example from the Nigerian Continental Slope. Marine Geology, 240(1-4), 235-255. Publisher's official version : https://doi.org/10.1016/j.margeo.2007.02.012 , Open Access version : https://archimer.ifremer.fr/doc/00000/2610/