| Title | Recent Results of 'Deep-seated Geothermal Resources Survey' Project in the Kakkonda Geothermal Field, Japan |
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| Authors | Toshiyuki Tosha, Kazuo Koide, Takao Ohminato, Kohei Akaku and Nobuo Doi |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | Deep geothermal reservoir, Kakkonda geothermal field, Flow test, Collapsing method, Natural state simulation |
| Abstract | During flow tests conducted at the well WD-1b in the Kakkonda geothermal area, geothermal fluid from a deep reservoir was successfully produced. The total flow rate and its vapor-liquid content at WD-1b suggest that a two-phase feeding condition is developed in the deep reservoir. The chemical characteristics of the water from well WD-1b are slightly different from those of the other deep production wells in Kakkonda possibly owing to high temperature and relatively low permeability of WD-1b. Although the stress field around WD-1a and WD-1b estimated from the DTF analysis is approximately in good agreement with the local stress field, no straightforward relationship between orientations of fractures and measured stress field. Isotopic analyses of fluid inclusions in quartz, tracer tests, and pressure monitoring using five shallow wells and a deep well give hydrologic property of the Kakkonda geothermal system. Using reservoir parameters obtained by the pressure monitoring, flow tests, and other various surface and borehole surveys, numerical simulations of the Kakkonda reservoir was conducted. The natural state simulation can reconstructs the observed temperature profile when the permeability in the shallower reservoir is two to three orders of magnitude higher than that of deep reservoir. The results of the collapsing analysis on microearthquake location confirms that the base of the seismogenic zone roughly corresponds to the isothermal contour of 300 to 350?C. The joint analysis of various types of electric resistivity measurement techniques, such as MAIL, VEMP, and conventional MT shows much higher resolution of resistivity structure in the vicinity of the well. Applicability of the synthetic fluid inclusion logging as a deep fluid sampler is confirmed by a series of laboratory tests. By exposing various types of test pieces of casing and pipings to the flow of geothermal field both in WD-1a and in the surface facilities, corrosion and erosion properties of metallic materials were investigated. The results obtained in the Kakkonda field will be used to make guidelines for the development of deepseated geothermal resources. |