NEDO {open_quotes}deep-seated geothermal resources survey{close_quotes} overview
An overview of NEDO {open_quotes}Deep-Seated Geothermal Resources Survey{close_quotes} is presented in this paper. The research project aims to confirm the existing conditions of deep geothermal reservoirs located in basement and intrusive rocks underneath shallow reservoirs (over 2,000 m deep from the surface). A 4,000 m class drillhole, Wedge-1 (WD-1), which will be the deepest and hottest (over 350{degrees}C) well in Japan, is now being drilled at the Kakkonda geothermal field located in northern Honshu, Japan. WD-1 has reached a depth of 3,729 m with an 8 1/2 inch hole following efforts to minimize lost circulation on the way through to shallow reservoirs located approximately in depths between 1,600 m to 2,150 m. Ten conventional and three oriented cores have been taken to a depth of 3,729 m. The boundary between Tertiary and Pre-Tertiary exists at a depth of 2,729 m. Neo-granite considered to be a possible heat source of the field appears over a depth of 2,860 m. The first appearance of contact metamorphic minerals and assemblages has become a good indicator to predict the depth of neo-granite top. The latest investigation with a Formation Micro Imager (FMI) revealed that drilling induced fractures oriented towards E-W to ENE-WSW directions at a depth interval from 1,505 m to 2,550 m. This indicates that the stress field has not changed, at least from the surface to a depth of 2,550 m. The results of long-term micro-earthquake monitoring indicates the existence of deep fracture systems in the western part of the Kakkonda geothermal field.
- OSTI ID:
- 175652
- Report Number(s):
- CONF-951037-; TRN: 95:008065-0064
- Resource Relation:
- Conference: Annual meeting of the Geothermal Resources Council, Reno, NV (United States), 8-11 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of Accomplishments of the past and challenges of the future. Transactions, Volume 19; PB: 604 p.
- Country of Publication:
- United States
- Language:
- English
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