Fracture systematics in and around well WD-1, kakkonda geothermal field, japan

• Published in: Geothermics Vol. 27; no. 5; pp. 609 - 629
• Main Authors: Kato, Osamu, Doi, Nobuo, Sakagawa, Yukihiro, Uchida, Toshihiro
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.1998
• Subjects: Boreholes; core; FMI log; fracture; geothermal; Geothermal fields; Geothermal logging; Geothermal prospecting; Japan; Kakkonda; Mechanical permeability; Remanence; remanent magnetization; Stress analysis; stress field; core; stress field; Kakkonda; Japan; geothermal; FMI log; remanent magnetization; fracture
• DOI: 10.1016/S0375-6505(98)00036-4
• ISSN: 0375-6505

Interpretation of FMI (Schlumbergers Fullbore Formation MicroImager) logs from well WD-1 and observation of spot cores from well WD-1 in the Kakkonda geothermal field have provided important clues about the nature and configuration of the fracture networks controlling circulation of high-temperature hydrothermal fluid. The fractures comprise four groups: (1) fractures striking NW, (2) high-angle fractures striking NE to E, (3) low-angle fractures striking N, and (4) low-angle fractures striking E. Most permeable fractures in the shallow (<1500 m depth) and deep reservoirs are of group 3, and likely reflect reverse faulting in the modern stress field. Low-angle, group 4 fractures are also permeable, and may have formed in the stress field that existed prior to 0.2±0.1 Ma. Distributions and densities of fractures are comparable in the shallow and deep reservoirs; the temperature difference between the reservoirs is independent of these variables.