Geological Analysis of the Kakkonda Geothermal Reservoir

Abstract

Detecting the distribution of permeable fractures in order to develop the geothermal reservoirs successfully is one of the most important part of analysis. And. it is also useful to know the fracture's genesis in order to estimate the distribution of the fracture in the poorly surveyed field. In this paper. fracture distribution and its genesis will be discussed in connection with a geological subsidence. folding. and magma intrusion. Kakkonda ( Takinoue ) geothermal field is located in Iwate Prefecture. Japan ( Fig. 1 ). and is a hot water dominated geothermal resevoir. A 50MW geothermal electric power plant was put into operation in 1978 by JMC and Tohoku Electric Power Co.• Ltd.. The plant is operated by eighteen production wells of 890-1820m in depth. and all of the separated hot water is injected by sixteen reinjection wells of 520-1600m in depth. Seven production and seven reinjection wells have been newly drilled for another 50 MW geothermal power plant. These deep wells reveal the geological condition such as fractures. dykes. hornfels and temperature distribution in deeper depth.