�@	Deep subsurface temperature distribution patterns estimated from temperature logging data: Examples of 14 Major Geothermal Fields in Japan

Deep subsurface temperature distribution patterns estimated from temperature logging data: Examples of 14 Major Geothermal Fields in Japan

Shiro Tamanyu, Kenichi Nomura and Masao Yoshizawa

1996

vol. 47 (10), p. 485-548, 61 figs., 7 tables.

Keywords: geothermics, temperature distribution pattern, subsurface temperature, temperature logging, temperature profile, heat conduction, geothermal area, relaxation method, major geothermal areas

Abstract: Subsurface temperature contour maps at four levels (0, -500, -1000, -2000m above sea level) have been compiled on the basis of bore hole temperature logging data. The target field are based on 14 areas, two of which are the Kurikoma and Sengan areas where the Sunshine geothermal project "Confirmation study of the effectiveness of prospecting techniques for deep geothermal resources" was carried out. The other 12 areas include the Downstream of Dozangawa, Okiura, Western Teshikaga, Oku-Aizu, Ikedako,Yuzawa-Ogachi, Kurino-Tearai, Shimokita, Northern Azuma, Western Unzen, Minami-Kayabe, and Toyoha areas where the geothermal project "Geothermal development promotion survey project" was carried out by NEDO. These 12 areas can be sub-divided into two groups. The first 5 areas are the Kurikoma analogous areas which are characterized by clear topographical caldera features, and the remaining 7 areas are the Sengan analogous areas which are characterized by no topographical caldera features except for geological calderas.
�@The estimation of the deep subsurface temperatures was based on temperature logging data from shallow drill holes using the relaxation method for the purpose of obtaining a more accurate subsurface temperature distribution in the Hohi area where many drill holes exist (Tamanyu et al., 1995). This method was adopted to estimate the deep subsurface temperature in all of the 14 study areas. As a result, the subsurface temperature distribution patterns for all of the areas were calculated. Although the estimated temperatures have some error, the data are very useful for further resource assessment and extractions of more potential ares in the fields.