An advancement of measurement system for Fluid Flow Tomography method

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A Fluid Flow Tomography (FFT) method is an exploration method to visualize the dynamic behavior of fluid resources for example oil, geothermal fluid and ground water etc. This method is the hybrid exploration method that can grasp fluid behavior by observing the transient change of both resistivity and streaming potential which occurs when a subsurface fluid flows. In order to obtain observed data and to analyze the data using the FFT method in real time, the development of the portable measurement system that a high speed sampling is possible in a field and the development of a control program are necessary. In this study, the following research about the advancement of the measurement system of the FFT method was carried out.The development of the measurement system was repeated many times from 2005.Finally the compact measurement system which uses the A/D module of 32 channels was developed in 2007. This measurement system is almost half of the prototype system in size, and the simultaneous measurement of the 256 channel is possible by using this system. The development of data analysis program was investigated in parallel with the development of the measurement system. Three-dimensional inversion programs of both resistivity and self potential method were developed.By using new measurement system, the FFT surveys were carried out around the Yamakawa geothermal power plant in Ibusuki, Kagoshima prefecture, Japan. A preliminary survey was carried out at the power station yard in June, 2007. As a result, a remarkable streaming potential change during injection was able to be observed. A full-scale FFT survey was carried out around the power station in December, 2007. As a result, the location of fault in relation to geothermal reservoir and the direction of subsurface fluid flow were able to be estimated.