Petrophysical Properties of Natural Gas Hydrates-Bearing Sands and Their Sedimentology in the Nankai Trough     

Takashi Uchida  Takashi Tsuji 《Resource Geology》2004,54(1):79-87

Abstract. The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys and drilling site-survey wells conducted by the MTI in 1997, 2001 and 2002 have revealed subsurface gas hydrate at a depth of about 290 mbsf (1235 mbsl) in the easternmost part of Nankai Trough. The MITI Nankai Trough wells were drilled in late 1999 and early 2000 to provide physical evidence for the existence of gas hydrate. During field operations, continuous LWD and wire-line well log data were obtained and numerous gas hydrate-bearing cores were recovered. Subsequence sedimentologic and geochemical analyses performed on the cores revealed important geologic controls on the formation and preservation of natural gas hydrate. This knowledge is crucial to predicting the location of other hydrate deposits and their eventual energy resource. Pore-space gas hydrates reside in sandy sediments from 205 to 268 mbsf mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space hydrates within moderate to thick sand layers. Gas hydrate-bearing sandy strata typically were 10 cm to a meter thick. Gas hydrate saturations are typically between 60 and 90 % throughout most of the hydrate-dominant sand layers, which are estimated by well log analyses as well as pore water chloride anomalies.
It is necessary for evaluating subfurface fluid dlow behavious to know both porosity and permeability of gas hydrate-bearing sand to evaluate subsurface fluid flow behaviors. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 40 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata.  相似文献   

Diffuse carbon dioxide emissions from hidden subsurface structures at Asama volcano,Japan     

Masaaki Morita  Toshiya Mori  Ryunosuke Kazahaya  Hiroshi Tsuji 《Bulletin of Volcanology》2016,78(3):17

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Chaos in cosmic ray air showers     

Takashi Kitamura  Soji Ohara  Takeharu Konishi  Katsufumi Tsuji  Michiyuki Chikawa  Wasaburo Unno  Isao Masaki  Kenji Urata  Yukihiro Kato 《Astroparticle Physics》1997,6(3-4):279-291

Unexpected chaotic features are found in time series of arrival time intervals of successive air showers with (E > 3 × 10¹⁴ eV). Over 99 % of air shower arrival time intervals obey the Poisson distribution law representing stochastic behaviors, but occasionally there are air showers showing real chaotic behaviors as distinguished from both random and colored noises. With two systems of the Kinki university installations, we found 13 cases showing chaotic time series in 3.36 yr with the system-1 and the 1.37 yr with the system-2. Five out of 10 chaotic air showers of the Kinki installation are detected during the same time zone also by the Osaka City university installation which is at 115 km distance from the Kinki one. In a remarkable example of September 19, 1991, the correlation dimension was observed to have dropped from about 4 to the minimum of 1.3 and recovered smoothly in about 38 h. The chaos structure in this case is detected in nearly the same time zone at the Ohya station of the Institute for Cosmic Ray Research, University of Tokyo, which is separated from the Kinki one by 460 km. Formation of chaos structure due to energetic cosmic ray dust particles is suggested. Progress of cosmic ray physics may be expected with the study of air showers marked with chaos.  相似文献   

Intrinsic properties of carbon stars. I. Effective temperature scale of N-type carbon stars     

Takashi Tsuji 《Journal of Astrophysics and Astronomy》1981,2(1):95-113

It is shown that the infrared flux method for determining stellar effective temperatures (Blackwell and Shallis 1977; Blackwell, Petford and Shallis 1980) can be applied to cool carbon stars. Although the spectra of cool carbon stars are highly line blanketed, the spectral region between 3 and 4 μm (L-band in the infrared photometry system) is found to be relatively free from strong line absorption. The ratioR _L of bolometric flux toL flux can then be used as a measure of effective temperature. On the basis of the predicted line-blanketed flux based on model atmospheres, with an empirical correction for the effect of 3 μm absorption due to polyatomic species (HCN, C₂H₂), it is shown thatR _L is roughly proportional to T³ _eff. The high sensitivity ofR _L to T_eff makes it a very good measure of effective temperature, and the usual difficulty due to differential line blanketing effect in the analyses of photometric indices of cool carbon stars can be minimized. It is found that the majority of N-type carbon stars with small variability (SRb and Lb variables) are confined to the effective temperature range between 2400 and 3200 K, in contrast to M-giant stars (M0 III - M6 III, including SRb and Lb variables) that are confined to the effective temperature range between 3200 and 3900 K. The effective temperatures based on the infrared flux method show good agreement with those derived directly from angular diameter measurements of 5 carbon stars. On the basis of the new effective temperature scale for carbon stars, it is shown that the well known C-classification does not represent a temperature sequence. On the other hand, colour temperatures based on various photometric indices all show good correlations with our derived effective temperatures. An erratum to this article is available at .  相似文献