Journal of the Geothermal Research Society of Japan
Online ISSN : 1883-5775
Print ISSN : 0388-6735
ISSN-L : 0388-6735
Volume 27, Issue 4
Displaying 1-6 of 6 articles from this issue
  • Preface for a Lecture Note on Geothermal Heat Pump System
    Yuichi NIIBORI
    2005 Volume 27 Issue 4 Pages 259-262
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
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  • Structure and Characteristics of Ground Source Heat Pump
    Yoshiro SHIBA
    2005 Volume 27 Issue 4 Pages 263-272
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
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  • Miyuki YOSHIKAWA, Yasuaki SUDO, Hideharu MASUDA, Shin YOSHIKAWA, Sachi ...
    2005 Volume 27 Issue 4 Pages 275-292
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    We inferred a geothermal structure of the Otake-Hatchobaru area based on the three-dimensional seismic velocity structure. A low Vp and Vs region related with the fracture zone at 1 km depth is located at the Otake-Hatchobaru area. Beneath this low Vp and Vs region, a high Vp and high Vs region surrounding a low Vp and high Vs region was found at 3.5 km depth, which is correlated to the granitic basement rocks and their intrusions. The low Vp and high Vs region at 3 km depth is related with the horizontally distributed fracture zone. A high Vp region was revealed at the depths of 5 km except for a part just under the Otake-Hatchobaru area. For the high Vp and low Vs region, we suggest a partial melting zone and a transporting zone of molten fraction. Just under the Otake-Hatchobaru area there is a low Vp and low Vs region at 5 km depth. The low Vp and Vs region continues to 8 km depth. And a low Vp and Vs region was found at 11 km depth to the south of Kuju Volcano. The low Vp and Vs regions are probably related to a recent magmatic body for Kuju Volcano. Therefore, the geothermal structuree at Kuju Volcano imaged from the seismic velocity structure may play an important role in geothermal energy of the Otake-Hatchobaru geothermal area.
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  • Toshiaki TANAKA, Shinichi KOSHI, Patricia MOLINA, Ryuichi ITOI, Tatsuy ...
    2005 Volume 27 Issue 4 Pages 293-305
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    For analysis of the hydrological connectivity between production and reinjection wells in the Kakkonda geothermal field, tracer tests were performed in 2002. In the tracer test, two different types of tracer were injected at respective reinjection well-116 and 136, and tracer return was examined by repeated sampling of water at 26 production wells. The results were analyzed with the multi-flowpath model to evaluate the magnitude of hydrological connectivity among the wells used in the tracer test, and to understand the flow behavior of reinjected water. Satisfactory results were obtained with a two-flowpath model for most production wells. Comparison of fluid velocities in each flowpath and the directions between the main feed points of production and reinjection wells indicated a possibility that some production wells are hydrologicaly connected to each other through the same fracture system. Tracer return are divided into two groups on the basis of mean-arrival-time, and amount of reinjected water return to production zone is appreciable for those with longer arrival time.
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  • Yoshimi IWATA, Toshifumi KOBAYASHI, Genzaburou FUKAYA, Keiichi YOKOHAR ...
    2005 Volume 27 Issue 4 Pages 307-320
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    An advantage of geothermal heat pump system (i.e., ground-coupled heat pumpp system with borehole) resulting from groundwater flow has been evaluated in Omachi and Iiyama Service Stations of Chubu Electric Power Co., Inc. In Japan, it is well-known that huge amount groundwater exists with the temperature of 10∼15°C. In order to design a geothermal heat pump with higher reliability, we should consider the ground heat deriving not only from heat conduction but also from groundwater flow. At present, the drilling cost in Japan is two or three times higher than that in Europe and USA. This matter directly raises the initial cost of geothermal heat pump system installation in Japan. Some reports have suggested the advantage of groundwater flow on subsurface heat extraction rate, which may affect on the design of geothermal heat pump. However, field experiments on this topic have not sufficiently been conducted. In our experiments, the geothermal heat pump system is supplied heat from boreholes of 100 m or 70 m deep, in which U-tubes are installed. As results of Omachi site experiments, the filling material (i.e., water, silica sand or cement) of the borehole affected on thermal response in heat extraction, although a heat-extraction-rate higher than 170 W/m was recorded in a steady state for any filling material. Based on the observation results in the observation wells, the groundwater flow velocity in Omachi-site was estimated to be 1.4×10-4 m/s in Darcy fluid flow velocity. On the other hand, in Iiyama site, the flow velocity of groundwater was in the order of 10-7 m/s. Though its velocity is remarkably smaller than that of Omachi site, groundwater flow in Iiyama site also caused high efficiency of the heat exchanger in a limited time-period.
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  • Tetsuya YAHARA, Hiroki SAITO, Ryuichi ITOI, Tatsuya MOTOYAMA
    2005 Volume 27 Issue 4 Pages 321-336
    Published: October 25, 2005
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Well H-30 started periodic decrease and recovery of its productivity since March 2002. The well had, then, lost the productivity such that it can not maintain wellhead pressure high enough to be connected to the two-phase flow pipeline network that transports the fluid to the main separator by the power station. A schematic reservoir model in the vicinity of the well was developed to explain these fluctuations using the results of well characteristics measurements, geochemical monitoring of produced fluids, production logging and tracer tests. The production history of well H-30 was divided into three periods on the basis of its productivity performance. The fluctuation in productivity was attributed to the excessive inflow of the separated water reinjected at wells near well H-30. Reducing the reinjection rate at nearby wells and/or the rate of mass production at well H-30 were recommended for stable production of well H-30.
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