| Title | Permeable Fractures and In-Situ Stress at the Kakkonda Geothermal Field, Japan |
|---|---|
| Authors | Osamu Kato, Takashi Okabe, Satoshi Shigehara, Nobuo Doi, Toshiyuki Tosha and Kazuo Koide |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | fractures, stress, core, micro-earthquake, oxygen isotopes, Kakkonda geothermal field |
| Abstract | Fourteen spot cores, many logs and micro-earthquake study reveal the fracture distribution and stress orientation around NEDOís well WD-1 continuously at northwest Kakkonda. This field has many fractures between the surface and ~3000m with various strikes and dips. The d18O value of the rock crystals within veins indicates whether the fracture is permeable or not. The permeable zone corresponds with the distribution of the open fractures independently of the fracture density. These fractures have been formed recently and some time ago. The permeable fractures are not necessarily formed in in-situ stress conditions at the present time. Permeable fractures formed some time ago keep opening and/or re-open under present stress conditions. |