Detection of free gas and gas hydrate based on 3D seismic data and cone penetration testing: An example from the Nigerian Continental Slope
| Autor: | Nabil Sultan, Jean-Louis Colliat, M. Voisset, Tania Marsset, V. Curinier, E. Cauquil, A. M. Vernant |
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| Jazyk: | angličtina |
| Rok vydání: | 2007 |
| Předmět: |
010504 meteorology & atmospheric sciences
Free gas Clathrate hydrate Mineralogy Effective medium theory 010502 geochemistry & geophysics Oceanography 01 natural sciences chemistry.chemical_compound Pore water pressure Geochemistry and Petrology Calibration Gas hydrate P-wave 14. Life underwater Piezocone 0105 earth and related environmental sciences geography geography.geographical_feature_category Continental shelf Geology chemistry Cone penetration test Carbonate Niger delta |
| Zdroj: | Marine Geology (0025-3227) (Elsevier), 2007-06, Vol. 240, N. 1-4, P. 235-255 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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