Induction Methods In Prospecting For Hot Water

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Journal Article: Induction Methods In Prospecting For Hot Water

It is commonly observed that in areas where abnormally heated water is rising to the surface, the electrical conductivity of the ground is significantly higher than in adjacent rocks. This has been the basis for the use of direct-current electrical prospecting methods in the search for an evaluation of geothermal power prospects. However, it can be argued theoretically that induction electromagnetic prospecting methods should be more effective in searching for conductive zones than direct current methods. We have used four electromagnetic methods in the evaluation of geothermal prospects: the audio-frequency magneto-telluric method, the two-coil profiling method, the two-coil frequency-domain sounding method, and the coil/wire time-domain sounding method. The audio-frequency magneto-telluric method is a very simple means for reconnaissance to depths of a few hundred meters. The two-loop profiling method provides high resolution for conductive zones within the first 20 or 30 meters of the surface, and may be used in detailing the surface expression of hyperthermal manifestations. The two-loop sounding method may be used to measure conductivities to a depth of 1 or 2 kilometers, even when the surface resistivity is too high to allow the use of direct-current methods. The wire/coil method may be used to map the source of anomalous heat into the lower crust and upper mantle.

G. V. Keller

Published Journal 
Geothermics, 1970



G. V. Keller. 1970. Induction Methods In Prospecting For Hot Water. Geothermics. (!) .