Model-Dependence of Size and Position of Heat Source in a Geothermal Reservoir

Abstract

This paper describes effects of boundary conditions on a geothermal reservoir analysis, using a porous model and data from Takenoyu geothermal field, in Kumamoto prefecture, Japan. The conclusions are as follows :(1) Under the assumption that the vertical length is 1.0km and there is a horizontal heat source on the bottom, the estimation error of temperature distribution in a case of the horizontal length of 2.5km almost agrees with the case of 5.0km. In the both cases, the heat source length of 1.0km gives the minimum estimation error between the calculation and the observation data.(2) When the heat source is assumed to be on the bottom or the center axis, the calculation agrees with the temperature data in the range from ground surface to 400m depth level. However, the latter calculation disagrees with the data in the range deeper than 400m.(3) Performance index evaluating differences between field data and model calculations should be defined not only by temperature, but also mass and heat discharges at the surface, in order to identify the size and position of the heat source.