TY - CONF
T1 - Gas hydrate and free gas accumulations in the Kumano forearc basin
T2 - 23rd Formation Evaluation Symposium of Japan 2017
AU - Chhun, Chanmaly
AU - Kioka, Arata
AU - Jia, Jihui
AU - Tsuji, Takeshi
N1 - Funding Information:
The seismic data was provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). This study was supported by the Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid for Scientific Research on Innovative Areas (no. JP15H01143). C.C. gratefully acknowledges for the scholarship program of ASEAN University Network/Southeast Asia Engineering Education Development Network (AUN/SEED-Net) for supporting her three year PhD study at Kyushu University. A.K. is currently funded by the Austrian Science Fund (FWF nr. P29678). J.J. and T.T are grateful to Cross-ministerial Strategic Innovation Promotion (SIP) program. We use well logging data provided by the International Ocean Discovery Program (IODP). A highly appreciation is also given to Madagascar, an open source software of seismic data processing, for developing the automatic velocity picking algorithm.
Publisher Copyright:
© 23rd Formation Evaluation Symposium of Japan 2017. All rights reserved.
PY - 2017
Y1 - 2017
N2 - To better define the accumulations of gas hydrates and free gases in the Kumano forearc basin which is located above accretionary prism in the Nankai margin off the Kii peninsula, Japan, we performed a high-resolution seismic velocity analysis to 3D seismic data using the method of conventional semblance spectra via automatic velocity picking algorithm. The results revealed that gas hydrate-bearing sediments above bottom-simulating reflector (BSR) and free gas-bearing sediments below BSR are characterized by P-wave velocities of 1900 - 2500 m/s, and 1000 - 1800 m/s, respectively. Gas hydrates are highly concentrated around the rim of the outer ridge where faults are densely developed, whereas free gas reservoirs are widely distributed below BSRs and are considerably high above ridge topography, which is considered as a structural trap for gas reservoirs. Then, the velocity model was converted into a gas hydrate and free gas saturation model using Archie's equations and rock physics models. The results indicated that saturation of gas hydrates and free gases ranges from 0 to 50% and 0-20% in the pore space, respectively. In addition, based on the velocity model of gas hydrates and free gas distribution, we suggested that gas hydrates concentrated due to the free gas influx which migrated upward through steeply dipping strata and faults or fractures cutting through the basin. Therefore, these factors generated by intensive tectonic movements in the plate subduction zone controlled the distribution and saturation pattern of gas hydrate and free gas formations.
AB - To better define the accumulations of gas hydrates and free gases in the Kumano forearc basin which is located above accretionary prism in the Nankai margin off the Kii peninsula, Japan, we performed a high-resolution seismic velocity analysis to 3D seismic data using the method of conventional semblance spectra via automatic velocity picking algorithm. The results revealed that gas hydrate-bearing sediments above bottom-simulating reflector (BSR) and free gas-bearing sediments below BSR are characterized by P-wave velocities of 1900 - 2500 m/s, and 1000 - 1800 m/s, respectively. Gas hydrates are highly concentrated around the rim of the outer ridge where faults are densely developed, whereas free gas reservoirs are widely distributed below BSRs and are considerably high above ridge topography, which is considered as a structural trap for gas reservoirs. Then, the velocity model was converted into a gas hydrate and free gas saturation model using Archie's equations and rock physics models. The results indicated that saturation of gas hydrates and free gases ranges from 0 to 50% and 0-20% in the pore space, respectively. In addition, based on the velocity model of gas hydrates and free gas distribution, we suggested that gas hydrates concentrated due to the free gas influx which migrated upward through steeply dipping strata and faults or fractures cutting through the basin. Therefore, these factors generated by intensive tectonic movements in the plate subduction zone controlled the distribution and saturation pattern of gas hydrate and free gas formations.
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M3 - Paper
AN - SCOPUS:85051728800
Y2 - 11 October 2017 through 12 October 2017
ER -