TY - JOUR
T1 - Characterization of hydrate and gas reservoirs in plate convergent margin by applying rock physics to high-resolution seismic velocity model
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. JP17H05318 ), a Grant-in-Aid for Scientific Research (S) (no. JP15H05717 ), and a Grant-in-Aid for Science Research B (No. JP15H02988 ). C.C. and T.T. gratefully acknowledge 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:
© 2017 Elsevier Ltd
PY - 2018/4
Y1 - 2018/4
N2 - Gas hydrates are widely distributed in the Kumano forearc basin, which is located above accretionary prism in the Nankai margin off the Kii peninsula, Japan. Bottom-Simulating Reflector (BSR) at the base of gas hydrate stability zone has been imaged as a strong acoustic impedance contrast on the reflection seismic profiles. In order to better define the accumulations of gas hydrates and free gases, we performed a high-resolution seismic velocity analysis to 3D seismic data using a method of conventional semblance spectra via automatic velocity picking algorithm. The results revealed that gas hydrate-bearing sediments above the BSR and free gas-bearing sediments below the BSR are characterized by P-wave velocities of 1900–2500 m/s and 1000–1800 m/s, respectively. Then, the velocity model was converted into gas hydrate and free gas saturation using rock physics approaches. The results indicated that saturation of gas hydrates ranges from 0% to 45% in the pore space, and highly concentrated around the outer ridge where faults are densely developed. Additionally, concentrations of free gas ranging from 0% to 20% in the pore space are widely distributed below BSRs and are considerably high above ridge structure generated by displacement of large fault splayed from the deep plate boundary décollement. Based on these results, we suggest that the gas hydrates concentrated due to the free gas influx which migrated upward through the steeply dipping strata and faults (or fractures) cutting through the basin. The accumulations of gas and/or hydrates are further controlled by fault movements in the accretionary prism beneath the forearc basin. Therefore, these factors generated by intensive tectonic movements in the plate subduction zone control the distribution and saturation pattern of gas hydrate and free gas formations.
AB - Gas hydrates are widely distributed in the Kumano forearc basin, which is located above accretionary prism in the Nankai margin off the Kii peninsula, Japan. Bottom-Simulating Reflector (BSR) at the base of gas hydrate stability zone has been imaged as a strong acoustic impedance contrast on the reflection seismic profiles. In order to better define the accumulations of gas hydrates and free gases, we performed a high-resolution seismic velocity analysis to 3D seismic data using a method of conventional semblance spectra via automatic velocity picking algorithm. The results revealed that gas hydrate-bearing sediments above the BSR and free gas-bearing sediments below the BSR are characterized by P-wave velocities of 1900–2500 m/s and 1000–1800 m/s, respectively. Then, the velocity model was converted into gas hydrate and free gas saturation using rock physics approaches. The results indicated that saturation of gas hydrates ranges from 0% to 45% in the pore space, and highly concentrated around the outer ridge where faults are densely developed. Additionally, concentrations of free gas ranging from 0% to 20% in the pore space are widely distributed below BSRs and are considerably high above ridge structure generated by displacement of large fault splayed from the deep plate boundary décollement. Based on these results, we suggest that the gas hydrates concentrated due to the free gas influx which migrated upward through the steeply dipping strata and faults (or fractures) cutting through the basin. The accumulations of gas and/or hydrates are further controlled by fault movements in the accretionary prism beneath the forearc basin. Therefore, these factors generated by intensive tectonic movements in the plate subduction zone control the distribution and saturation pattern of gas hydrate and free gas formations.
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U2 - 10.1016/j.marpetgeo.2017.12.002
DO - 10.1016/j.marpetgeo.2017.12.002
M3 - Article
AN - SCOPUS:85037719761
SN - 0264-8172
VL - 92
SP - 719
EP - 732
JO - Marine and Petroleum Geology
JF - Marine and Petroleum Geology
ER -