Study of geothermal water circulation

Research Project

Project/Area Number	59460041
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	気象・海洋・陸水学
Research Institution	Kyoto University
Principal Investigator	YUSA Yuki Kyoto University, Faculty of Science; Associate Professor, 理学部, 助教授 (90025403)
Co-Investigator(Kenkyū-buntansha)	KAWANO Tamio Oita University, Faculty of Education; Associate Professor, 教育学部, 助教授 (00040725) KAMIYAMA Kokichi Kyoto University, Faculty of Science; Research Associate, 理学部, 助手 (70135507) KITAOKA Koichi Kyoto University, Faculty of Science; Research Associate, 理学部, 助手 (30093230)
Project Period (FY)	1984 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥7,800,000 (Direct Cost: ¥7,800,000) Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000) Fiscal Year 1985: ¥1,000,000 (Direct Cost: ¥1,000,000) Fiscal Year 1984: ¥5,800,000 (Direct Cost: ¥5,800,000)
Keywords	Geothermal Phenomena / Density of Land Water / 地熱流体の循環
Research Abstract	1. Measurement of densities of various geothermal waters was conducted by a Digital Density Meter; but satisfactory results have not been got yet, because it took many hours for arrangement of the apparatus. Nevertheless, densities of geothermal waters, groundwaters and rain waters in Japan and some land waters from Antarctica and South America were measured, and relationships between densities and electric conductivities were obtained. From now on, we will try to develop the measurment at higher temperatures. 2. Discharges of water, steam and heat with chemical constituents were observed in the Beppu Geothermal Field. Through it, the horizontal sphere of the subsurface ateam zone was clarified. It is also noted that the ratio of steam in total discharge is increasing during the last 25 years. 3. The compilation of data of subsurface temperatures in Middle Kyushu and San'in District revealed that the basic geothermal gradient is about 6゜C/100m. The analysis suggests a possibility that ge … More othermal activities in those area can be formed through the regional circulation of water under the foregoing geothermal gradient. It was also shown that the shallower the zone of large permeability, the narrower the surface area of the high temperature. 4. As observed in the Beppu Geothermal Field, the subsurface steam zone is formed by the evaporation of geothermal water. In such a field, two-phase flow accompanied by phase change may play an important roll in the circulation of geothermal fluid. Thus, an theoretical study of two-phase flow in porous medium was carried out, and fundamental equations were derived. Based on them, hydraulic characteristics of the system were investigated to clarify some features such as (1) hydraulic storativity is controlled by subsurface temperature, and (2) propagation of pressure change is affected by heat conduction. In addition, vertical circulation in two-phase system was investigated numerically using simplified equations; which gave some information on quantitative relationship between circulation and permeability etc.. Less