著者

安川 香澄 野田 徹郎

出版者

日本地熱学会

雑誌

日本地熱学会誌 (ISSN:03886735)

巻号頁・発行日

vol.39, no.4, pp.203-215, 2017-10-25 (Released:2018-04-25)

参考文献数

16

被引用文献数

2

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A criterion to evaluate possible influence of geothermal development onto nearby hot spring aquifer, based on geochemical characteristic of the aquifer, was developed in a form of decision tree. Hydraulic and thermal connection of a geothermal reservoir to nearby hot spring aquifer may be expressed by five types of simplified structure models, which are, identical thermal water-, seepage thermal water-, steam heated-, heat conduction- and independent- systems. Since interference of geothermal fluid production differs depend on such types, required monitoring items for protection of hot spring aquifers also differ for each type. The type of relationship between a specific geothermal reservoir and a nearby hot spring aquifer can be roughly estimated by temperature and anion characteristics of the hot spring waters for volcanic geothermal systems. In a former study, a criterion was developed based on five types of geochemical characteristics of hot spring waters. However, such a categorization was not quite successful when volcanic gas or CO2 gas was supplied to the aquifer or geometrical setting was not appropriate. Although hydraulic relationship is well described by five types, geochemical characteristics of hot springs are not well represented by five types only. Therefore in this study, a new criterion was developed by adding two new types, CO2 gas supply and volcanic gas supply types, resulting in seven types in total. Spatial arrangement of the target aquifer and geothermal reservoir is also taken into consideration. The threshold values in this criterion are based on data sets obtained from hot spring wells and natural geothermal manifestations all over Japan. Then the new criterion was applied to hot spring waters in Kuju region, Oita, Japan where three geothermal power plants are in operation. As a result, all seven types were identified for this region. It was found that hot springs of seepage thermal water type and steam heated type densely exist near geothermal power plants, suggesting that such hot spring type identification may be an effective tool for geothermal exploration. The new criterion, which helps to estimate effects of geothermal development onto each nearby hot spring aquifer and enables to protect hot springs against excess geothermal development, may be applied for other volcanic geothermal regions.

著者

野田 徹郎

出版者

公益社団法人 日本化学会

雑誌

化学と教育 (ISSN:03862151)

巻号頁・発行日

vol.64, no.8, pp.400-405, 2016-08-20 (Released:2017-02-01)

参考文献数

7

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大分県で地熱発電が盛んなのは地熱資源が豊富だからである。地熱資源の化学成分や同位体の組成は,水の起源が天水であり,地下に浸透した天水が火山活動と岩石との反応を被ってもたらされたものであり,その解析により地熱資源の形成過程を知ることができる。この地熱資源の探査にも化学成分は有効であり,地化学温度計は有効な定量的指標の一つである。地熱発電を持続的に行うためにも化学の情報は重要であり,化学的な処理によりトラブルを軽減することができる。また,温泉など環境への影響を回避するための考察にも役立つ。

著者

野田 徹郎

出版者

THE GEOTHERMAL RESEARCH SOCIETY OF JAPAN

雑誌

日本地熱学会誌 (ISSN:03886735)

巻号頁・発行日

vol.9, no.2, pp.133-141, 1987-04-25 (Released:2009-08-07)

参考文献数

7

被引用文献数

1

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An anion index, AI, is proposed as an indicator to estimate the proximity to the center of geothermal activity. AI, defined as following, is calculated from major anion composition of a hot spring water.AI=0.5×(SO4/Cl+SO4+Cl+SO4/Cl+SO4+HCO3) (unit: equivalents) AI is unity at the steaming ground where geothermal activity is highest. It gradually decreases with increasing a distance from the center of activity, with the appearance of Cl type thermal water, and with mixing of HC03 type water. AI is recommended as a practical qualitative indicator presenting degree of closeness to the center of geothermal activity, but should not be applied to thermal water from deeper wells, to volcanic fumaroles emitting HCl, or to springs originated from sea water.