This article explains about adsorbed gas, which is a unique state of natural gas stored in unconventional natural gas reservoirs, and also shows possibilities surveying it using geophysical techniques of exploration. The main state of coalbed methane in coal seams is the adsorbed gas and nearly a half of shale gas is stored as the same way. Our measurements of the amount of adsorbed gas in rock samples in the laboratory indicate that a siliceous shale rock of Onnagawa formation has the same performance to adsorb gas as shale rocks in the North America and a mud rock of the natural gas field in the South Kanto region of Japan has also enough performance to adsorb gas. The total amount of adsorbed gas is huge in the world and it must be a natural gas resource with high potential. As development of the adsorbed gas requires continuous production for longer periods than free gas, the technique to estimate the variation of gas production rate becomes important. Evaluation techniques of gas reserves and productivity using geophysical exploration methods can increase the amount of natural gas reserves. The distribution of adsorbed gas in the field must be acquired to develop it strategically. Any survey techniques have not been proposed to directly estimate the possible amount of adsorbing gas in reservoir. However, various ideas have been discussed to indirectly estimate the amount of adsorbed gas using logging tools.

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  When the safety of railway facilities and running vehicles are threatened by large shakings of ground motions during earthquakes, railway operators stop trains as soon as possible. After the safety of train operation are ensured by a cautious inspection patrol along the railway section following the rule decided in advance, the train operation is resumed. To confirm visually the damage of railway facilities and deformation of railway tracks in the inspection, it may take a lot of time. It is necessary to carry out the safety inspection more precisely and effectively, for shortening downtime of regular train operation. Therefore to comprehend exactly the characteristics of earthquake ground motions along the target railway, the rapid evaluation of the earthquake ground motions, not only at the points where the seismographs are installed at equal intervals but also at the other points on the railway, are strongly required.
  In this study, we adopted Miyazaki maglev test line, which has a total length of 7 km, located in the middle coast of Miyazaki prefecture, as a model railway. We tried to estimate the continuous linear S-wave velocity structures and earthquake ground motions along Miyazaki maglev test line. At first, we tried to estimate S-wave velocity structures at two sites where seismographs are installed, using the geophysical exploration such as surface wave exploration and array microtremor survey. Secondly, we estimated the continuous linear S-wave velocity structures on the model railway, based on the S-wave velocity structures estimated by the geophysical exploration method, using the H/V spectral ratios obtained by the high-dense microtremor measurement. Finally, we estimated the high-dense earthquake ground motions along Miyazaki maglev test line by the one-dimensional multiple reflection theory. We confirmed the validity of the continuous linear S-wave velocity structures and the estimated earthquake ground motions along Miyazaki maglev test line, through the comparison with the observed earthquake ground motions.

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  One of the key factors in the dissemination of ground heat exchanger systems is the installation of secure systems at each implementation point. The most important parameters for installing secure systems are the optimized depth and the number of heat exchange wells. For system optimization, one effective measure is to conduct numerical simulations of the estimated heat exchanger effectiveness of the geothermal heat pump system. Geological structures, the properties of groundwater, and the subsurface temperatures, for example, are essential input data for the numerical simulations. However, there is little information concerning subsurface temperatures. Thus, we have performed measurements of subsurface temperatures at 23 stations in the Saitama region, which is located in the central part of the Kanto plain. Thereafter, we have illustrated a numerical simulation for ground heat exchangers using the recent subsurface temperature data. Furthermore, we have discussed the regional characteristics of potential assessments for ground heat exchangers. The results are expected to be used as information prior to the installation of ground heat exchangers. For evaluating the potential assessments, we have developed a new method using an existing geological model with high spatial resolution and applied the method to the southeastern part of Saitama region. The results show that the potential in the plateau area located in the central part of the region is higher than in the lowland area in the eastern part.
  We conclude that our proposed method for the synthesis of subsurface temperature data and the evaluated potentials of ground heat exchangers can contribute to lower initial costs and the installation of secure systems.

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  The survey area was reclaimed approximately 100 years ago, and the historical records indicate the presence of buildings on multiple sites in the area. Even though these buildings have now been removed, it is important to locate the buried foundations and remnants so that construction can be planed to avoid any associated problems. A frequency domain electromagnetic method (EM method) was used to explore a subsurface structure to a depth of 5 m, allowing buried utilities discarded underground located in a large survey areas (360×190m). We measured along 3D survey lines with a total extent of approximately 10 km using the EM38 and EM31 instruments which can explore to a depth of 1.5 m and 5 m, respectively. We described two plan views calculated from the responses of in-phase and quad-phase. Four classes of buried utilities were defined according to the electromagnetic response: (1) small sized metal utilities at depths to a few tens centimeters, (2) large sized iron plates at depths to a few tens centimeters, (3) iron pipes at about 1 meter in depth, and (4) the foundations of buildings deeper than 2 meters. Based on these results, we located suitable excavation positions and attempted to remove the large buried utilities using a heavy industrial machine. We uncovered two iron plates (6×1.5 m) at a depth of 0.2 - 0.5 m as well as reinforced concrete foundations (23×2.5×0.35 m) at a depth of 2.6 m. Additionally, the electrical conductivity derived using the EM method was in good agreement with the electrical logging data conducted by penetration tests at 15 points in the survey area. The EM method was demonstrated to be effective in locating buried utilities and exploring geological structures to a depth of 5 m within a large survey area.

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  In order to analyze a lot of TEM data, an easy-to-use program incorporating Graphical User Interface (GUI) was developed. The new program named “Temtool” has a function of 1-D forward modeling that can calculate transient responses for multilayer structure using rectangular loop source. Also both Marquardt method and smoothness inversion were implemented for 1-D TEM inversion. In addition, 3-D view function to display three-dimensional distribution of observed data and analysis result. This function helps us to evaluate observed data and interpret analysis result effectively.

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[in Japanese]

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