Prof. Takeshi Tsuji (CO2 Storage Division at International Institute for Carbon Neutral Energy/ Faculty of Engineering Kyushu University ), Mr Andri Hendriyana (Post-doctoral Research Associate at I2CNER) and Kota Mukumoto, a master student in Graduate School of Engineering, Kyushu University revealed a large gas reservoir along the rift axis of a continental back-arc basin in the Okinawa Trough.
This study has been published on the online edition of science magazine in the United States, Geophysical Research Letters on 19th August 2019.
In the Okinawa Trough off southwestern Japan, hydrothermal circulation due to back-arc rifting 30 is active. Biogenic CH4 in discharging hydrothermal fluids at the Iheya North Knoll is derived 31 from outside the knoll; however, the location of the gas reservoir has not been identified. Here, 32 we applied automated velocity analysis to seismic reflection data to obtain a P-wave velocity 33 structure in high spatial resolution. The resulting profiles reveal large gas reservoirs as low34 velocity zones along the rifting axis (>5km for axis direction) around the Iheya North Knoll. The 35 main gaseous components in the reservoir could be CO2 and CH4. The heat flow inferred from 36 seismic profiles (i.e., depth of reflector) indicates that CH4 hydrate could be trapping the gas. 37 Furthermore, the heat flow is higher at the rifting axis and close to the knoll, reflecting the large 38 gas reservoir feeding the hydrothermal fluids in the discharging area at the knoll.
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Title: Large Gas Reservoir along the Rift Axis of a Continental Back-arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough
Authors: Kota Mukumoto, Takeshi Tsuji, Andri Hendriyana
Published online: 19 August 2019