Quantification of free gas in the Kumano fore-arc basin detected from borehole physical properties; IODP NanTroSEIZE drilling Site C0009

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doi: 10.1029/2010GC003284
Author(s): Doan, Mai-Linh; Conin, Marianne J.; Henry, Pierre; Wiersberg, Thomas; Boutt, David; Buchs, David; Saffer, Demian M.; McNeill, Lisa C.; Cukur, Deniz; Lin, Weiren
Author Affiliation(s): Primary:
Université Joseph Fourier, Institut des Sciences de la Terre, Grenoble, France
Université Aix-Marseille III, France
Deutsches GeoForschungsZentrum, Germany
University of Massachusetts Amherst, United States
Australian National University, Australia
Pennsylvania State University, United States
University of Southampton, United Kingdom
Pukyong National University, South Korea
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, Vol.12. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 23 refs.; illus., incl. 2 tables
Summary: The Kumano fore-arc basin overlies the Nankai accretionary prism, formed by the subduction of the Philippine Sea Plate beneath the Eurasian plate offshore the Kii Peninsula, SW Honshu, Japan. Seismic surveys and boreholes within the framework of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) project show evidence of gas hydrates and free gas within the basin. Here we use high-quality borehole sonic data from Integrated Oceanic Drilling Program (IODP) Site C0009 to quantify the free gas distribution in the landward part of the basin. The Brie theory is used to quantify gas content from sonic logs, which are calibrated from laboratory measurements on drill cores. First, we show that the sonic data are mainly sensitive to the fluid phase filling the intergranular pores (effective porosity), rather than to the total porosity that includes water bound to clay minerals. We then compare the effective porosity to lithodensity-derived porosity that acts as a proxy for total porosity. The combination of these two data sets also allows assessment of clay mineralogy of the sediments. Second, we compute free gas saturation and find a gas-rich interval that is restricted to a lithological unit characterized by a high abundance of wood fragments and lignite. This unit, at the base of the fore-arc basin, is a hydrocarbon source that should be taken into account in models explaining gas distribution and the formation of the bottom-simulating reflector within the Kumano fore-arc basin.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Accretionary wedges; Acoustical methods; Asia; Basins; Boreholes; Brie equations; Clay minerals; Eurasian Plate; Expedition 319; Far East; Fore-arc basins; Gas hydrates; Gas seeps; Geophysical methods; Geophysical profiles; Geophysical surveys; Honshu; IODP Site C0009; Integrated Ocean Drilling Program; Japan; Kii Peninsula; Kumano Basin; NanTroSEIZE; Nankai Trough; Natural gas; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Petroleum; Philippine Sea Plate; Plate tectonics; Seismic methods; Seismic profiles; Sheet silicates; Silicates; Subduction zones; Surveys; Tectonophysics; West Pacific
Coordinates: N332728 N332728 E1363209 E1363209
Record ID: 2013046506
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