https://repository.kopri.re.kr/handle/201206/5513 2026-04-18T22:28:54Z 2026-04-18T22:28:54Z A. Hachikubo O. Vereshchagina H Minami S. Yamashita A. Obzhirov Jin, Young Keun H. Shoji N. Takahishi H. Sakamami https://repository.kopri.re.kr/handle/201206/8446 2022-03-24T07:10:34Z 2012-01-01T00:00:00Z

Title: NATURAL GAS HYDRATE IN SUBSURFACE SEDIMENTS OBTAINED FROM OFFSHORE OF SAKHALIN ISLAND, SEA OF OKHOTSK ―MOLECULAR AND ISOTOPIC SIGNATURES OF HYDRATE-BOUND HYDROCARBONS Authors: A. Hachikubo; O. Vereshchagina; H Minami; S. Yamashita; A. Obzhirov; Jin, Young Keun; H. Shoji; N. Takahishi; H. Sakamami Abstract: Near-surface gas hydrates exist in the seepage sites of offshore Sakhalin Island, the Sea of Okhotsk. These sites often accompany with gas plumes from the sea floor. We investigated the molecular and stable isotope composition of hydrate-bound and dissolved hydrocarbons in pore water in subsurface sediments. More than ten gas seep sites have been discovered since 1990s in the north area of Lavrentyev seabed fault (NE Sakhalin Island) and hydrate-bearing sediments were recovered by using a gravity corer. Recently, Sakhalin Slope Gas Hydrate (SSGH) project was started in 2007 and we retrieved hydrate- bearing sediment cores from the southern area of Lavrentyev Fault in 2009-2011. We obtained the samples of hydrate-bound gas and dissolved gas in pore water on board, and we measured molecular and stable isotope compositions of them. Empirical classification of the methane stable isotopes; δ13C and δD indicated their microbial origin via carbonate reduction. Profiles of methane concentration in the pore water suggested a shallow SMI (sulfate-methane interface) and high methane flux from the deep sediment layer. SMI depth was estimated as 30-50cm from the sea floor in the case of hydrate- bearing cores, and around 2m from the sea floor in the case of gas-rich cores. Molecular compositions of hydrate-bound gas were almost the same in both northern and southern areas of Lavrentyev Fault. Stable-bound and dissolved hydrocarbons in pore water in subsurface sediments. More than ten gas seep sites have been discovered since 1990s in the north area of Lavrentyev seabed fault (NE Sakhalin Island) and hydrate-bearing sediments were recovered by using a gravity corer. Recently, Sakhalin Slope Gas Hydrate (SSGH) project was started in 2007 and we retrieved hydrate- bearing sediment cores from the southern area of Lavrentyev Fault in 2009-2011. We obtained the samples of hydrate-bound gas and dissolved gas in pore water on board, and we me

2012-01-01T00:00:00Z Satoshi Yamashita Nataliya Nikolaeva Nobuo Takahashi Hirotsugu Minami Akihiro Hachikubo Kazuya Tatsumi Alexander Derkachev Anatoly Obzhirov Jin, Young Keun Hitoshi Shoji Hirotoshi Sakagami https://repository.kopri.re.kr/handle/201206/5658 2022-03-24T07:12:07Z 2012-01-01T00:00:00Z

Title: Possible variation in methane flux caused by gas hydrate formation on the northeastern continental slope off Sakhalin Island, Russia Authors: Satoshi Yamashita; Nataliya Nikolaeva; Nobuo Takahashi; Hirotsugu Minami; Akihiro Hachikubo; Kazuya Tatsumi; Alexander Derkachev; Anatoly Obzhirov; Jin, Young Keun; Hitoshi Shoji; Hirotoshi Sakagami Abstract: The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea and Russia to investigate natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island. From 2009 to 2011, field operations of the SSGH-09, SSGH-10 and SSGH-11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in the sediment pore waters obtained during those cruises were measured to investigate the sulfate concentration-depth profile. Seventeen cores showed linear depth profiles of sulfate concentrations, whereas 8 cores and 2 cores showed the concave-up and - down profiles due to a sudden increase and decrease in the methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites.nd. From 2009 to 2011, field operations of the SSGH-09, SSGH-10 and SSGH-11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in the sediment pore waters obtained during those cruises were measured to investigate the sulfate concentration-depth profile. Seventeen cores showed linear depth profiles of sulfate concentrations, whereas 8 cores and 2 cores showed the concave-up and - down profiles due to a sudden increase and decrease in the methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites.

2012-01-01T00:00:00Z