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Magnetotelluric survey applied to geothermal exploration: An example at Seokmo Island, Korea  

Lee, Tae-Jong (Korea Institute of Geoscience and Mineral Resources (KIGAM))
Han, Nu-Ree (Seoul National University)
Song, Yoon-Ho (Korea Institute of Geoscience and Mineral Resources (KIGAM))
Publication Information
Geophysics and Geophysical Exploration / v.13, no.1, 2010 , pp. 61-68 More about this Journal
Abstract
A magnetotelluric (MT) survey has been performed to delineate deeply extended fracture systems at the geothermal field in Seokmo Island, Korea. To assist interpretation of the MT data, geological surveying and well logging of existing wells were also performed. The surface geology of the island shows Cretaceous and Jurassic granite in the north and Precambrian schist in the south. The geothermal regime has been found along the boundary between the schist and Cretaceous granite. Because of the deep circulation along the fracture system, geothermal gradient of the target area exceeds $45^{\circ}C/km$, which is much higher than the average geothermal gradient in Korea. 2D and 3D inversions of MT data clearly showed a very conductive anomaly, which is interpreted as a fracture system bearing saline water that extends at least down to 1.5 km depth and is inclined eastwards. After drilling down to the depth of 1280 m, more than 4000 tons/day of geothermal water overflowed with temperature higher than $70^{\circ}C$. This water showed very similar chemical composition and temperature to those from another existing well, so that they can be considered to have the same origin; i.e. from the same fracture system. A new geothermal project for combined heat and power generation was launched in 2009 in Seokmo Island, based on the survey. Additional geophysical investigations including MT surveys to cover a wider area, seismic reflection surveys, borehole surveys, and well logging of more than 20 existing boreholes will be conducted.
Keywords
fracture system; geothermal; magnetotelluric survey; Seokmo Island;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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1 Lee, T. J., Lee, S. K., Song, Y., and Uchida, T., 2006b, Use of Audio-band on the interpretation of magnetotelluric data: Mulli-Tamsa, 9, 261–270.
2 Gamble, T. D., Goubau, W. M., and Clarke, J., 1979, Magnetotelluric with remote reference: Geophysics, 44, 53–68.
3 Lee, S.-G., Kim, T.-K., Lee, J.-S., and Song, Y., 2006a, Rb-Sr Isotope geochemistry in Seokmodo granitoids and hot spring, Ganghwa: An application of Sr isotope for clarifying the source of hot spring: Journal of Petroleum Society of Korea, 15, 60–71.
4 Han, N., Nam, M. J., Kim, H. J., Lee, T. J., Song, Y., and Suh, J. H., 2008, Efficient three-dimensional inversion of magnetotelluric data using approximate sensitivities: Geophysical Journal International, 175, 477–485. doi:10.1111/j.1365-246X.2008.03894.x
5 Geotools Corporation, 1997, Geotools MT user's guide – A complete system for magnetotelluric interpretation: Geotools Corporation.
6 Lee, M. W., 1985, Jeju volcanic Island: Journal of Korean Earth Science Society, 6, 49–53.
7 Park, D.-W., and Lee, C.-B., 2007, Characteristics of micro-crack orientations in Mesozoic granites and granite dyke rocks from Seokmo-do, Ganghwagun: Journal of Petroleum Society of Korea, 16, 1–15.
8 Uchida, T., 1993, Smooth 2-D inversion for magnetotelluric data based on statistical criterion ABIC: Journal of Geomagnetism and Geoelectricity, 45, 841–898.
9 Kim, H.-C., and Song, Y., 2005, Characteristics of Geothermal Anomaly in South Korea: Proceedings,World Geothermal Congress, Antalya, Turkey, 24–29 April.