Japan Geoscience Union Meeting 2023

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS18] Gas hydrates in environmental-resource sciences

Mon. May 22, 2023 9:00 AM - 10:15 AM 102 (International Conference Hall, Makuhari Messe)

convener:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Shinsuke Aoki(The National Institute of Advanced Science and Technology), Chairperson:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Shinsuke Aoki(The National Institute of Advanced Science and Technology)

9:05 AM - 9:20 AM

[MIS18-01] Drilling survey on the shallow methane hydrate-bearing area off Joetsu, Sea of Japan.

*Mikio Satoh1, Kiyofumi Suzuki2, Hideyoshi Yoshioka1, CK22-03C Shipboard Scientific Party (1.Research Institute for Geo-Resources and Environment (GREEN), Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), 2.Energy Process Research Institute (EPRI), National Institute of Advanced Industrial Science and Technology (AIST))

Keywords:shallow methane hydrate, off Joetsu, Drilling survey, Geotechnical survey, The D/V Chikyu, wireline logging

Since 2013, marine geological and environmental survey for shallow methane gas hydrate production are conducting by the National Institute of Advanced Industrial Science and Technology (AIST) funded by METI (the Ministry of Economy, Trade and Industry, Japan). Since 2019, AIST started comprehensive research program for shallow methane gas hydrate, consist of production method development, exploration and environmental research for shallow methane hydrate-bearing area.
Geomechanical information of the hydrate-bearing sediments are important, because direct drilling method is proposed for natural gas recovery and production from shallow methane gas hydrate, which are occurred in shallow unconsolidated sediments bellow seafloor. Therefore we conducted geomechanical survey cruises on hydrate-bearing areas, off Sakata area in August 2021 (PS21 Research Cruise), and off Joetsu area in September 2022 (CK22-03C Research Cruise). In this presentation, we report the general information of the CK22-03C Research Cruise surveyed off Joetsu in 2022.
CK22-03C Research Cruise are conducted on off Joetsu area used by the D/V Chikyu belonging to the JAMSTEC, during 11days for drilling in total 23days in September 2022. We drilled 2 holes on southern part of Joetsu Knoll (JK), and 2 holes on northern part of Umitaka Spur (UTN). One hole is on mound bellow which methane hydrate occurred (MH site), another hole is on no-hydrate site (RE site), both Joetsu Knoll and Umitaka Spur. Drilling depth are 155 mbsf at JK-MH site (WD 981 m), 122 mbsf at UTN-MH site (WD 916 m), 144 mbsf at JK-RE site (WD 984 m) and UTN-RE site (WD 925 m), and all of those depth are deeper than estimated depth of base of gas hydrate stability (BGHS).
Sediment core sampling and wireline logging are successfully conducted on all of 4 holes. Continuous sediment core of 99 m and 90 m length bellow seafloor are recovered at JK-RE site and UTN-RE site, but limited recovery at other depth because of hard sediment, such as solid gas hydrate and carbonate rocks, and limited ship times. Total recovered length of cores are 32 m at JK-MH site, and 12 m at UTN-MH site. Recovered sediment core are immediately sampled for gas and interstitial water analysis, after that, nondestructive measurement such as X-ray CT scan and multi sensor core truck (MSCL) are conducted. After measurement, cores are sorted to whole-round core for onshore geomechanical soil test and split core for onboard description, sub-sampling and measurements, based on XCT-images.
Wireline logging were conducted at all 4 holes, at where continuous data, such as velocity, resistivity, natural gamma ray, NMR, density, etc. from seafloor to 110 or 140 mbsf were acquired, however some data are lacked because of problem of logging tools and limited ship times.
Onboard geomechanical measurement data, onshore geomechanical soil test data, wireline logging data are analyzed for geomechanical property evaluation of hydrate-bearing or around hydrate sediments. Geochemical and sedimentological analysis, and dating data (from tephra, microfossil, carbon isotope, etc.) will be use as geological background data for geomechanical property evaluation.
This study was conducted as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).