Geophysics and Geophysical Exploration (지구물리와물리탐사)

Korean Society of Earth and Exploration Geophysicists (한국지구물리·물리탐사학회)
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Modeling of SP responses for geothermal-fluid flow within EGS reservoir

EGS 지열 저류층 유체 유동에 의한 SP 반응 모델링

  • Song, Seo Young (Department of Energy and mineral Resources Engineering, Sejong University) ;
  • Kim, Bitnarae (Department of Energy and mineral Resources Engineering, Sejong University) ;
  • Nam, Myung Jin (Department of Energy and mineral Resources Engineering, Sejong University) ;
  • Lim, Sung Keun (Korea Rural Community Corporation)
  • Received : 2015.09.22
  • Accepted : 2015.11.27
  • Published : 2015.11.30
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Abstract

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

자연 전위(SP, self-potential)의 발생에는 여러 요인이 있으나 이 연구에서는 지하수의 유동에 의해 자연적으로 발생하는 유동 전위(streaming potential) 또는 전기역학적 전위(electrokinetic potential)에 대해 주로 논의한다. 유동 전위는 다공질 매질에서의 물의 흐름에 의해 인공적인 전류원 없이 전류가 발생하여 야기된 전위이다. 기존의 유동 전위를 이용한 지열 저류층 해석에서는 지표면 전위 분포 계산을 위해 일반적으로 시추공에서 주입되거나 생산되는 지하수로부터 발생하는 SP 이상만을 고려하였고, 온도 차이가 나는 지열 저류층에서의 지열수 순환에 따라 발생할 수 있는 SP에 대한 수치 모델링에는 한계가 있었다. 이에 따라 사면체 요소를 바탕으로 한 3차원 전기비저항 유한요소법에 기초하여 지열 저류층 내에서의 주입정, 생산정에 의한 SP 이상뿐만 아니라 지열 저류층에서의 지열수 순환에 따른 SP 이상까지 고려할 수 있는 알고리듬을 개발하였다. 본 논문에서는 개발한 알고리듬을 검증 한 후, 간단한 지열 저류층 모델에 지열수 주입과 양수의 효과에 의한 SP 이상대의 SP 반응을 분석하였다. 향후 개발한 알고리듬을 이용하여 지층의 물성을 고려한 지열수 유동 속도 등도 고려함으로써 보다 심도 있게 지열 저류층 SP 반응을 분석하고자 한다.

Keywords

References

  1. Kang, H. J., Cho, I. K., Kim, J. H., and Yong, H. H., 2014, SP Monitoring at a Sea Dike, Near Surface Geophysics, 12, 83-92.
  2. Cioni, R., Fanelli, G., and Guidi, M., 1992, Lake Bogoria hot springs (Kenay): geochemical features and geothermal implications, Journal of Volcanology and Geothermal Research, 50, 231-246. https://doi.org/10.1016/0377-0273(92)90095-U
  3. Corwin, R. F., and Hoover, D. B., 1979, The self-potential method in geothermal exploration, Geophysics, 44, 226-245. https://doi.org/10.1190/1.1440964
  4. Ishido, T., and Mizutani, H., 1981, Experimental and theoretical basis of electrokinetic phenomena in rock-water system and its application to geophysics, J. Geophys. Res., 86, 1763-1775. https://doi.org/10.1029/JB086iB03p01763
  5. Ishido, T., Kikuchi, T., and Sugihara, M., 1989, Mapping thermally driven upflows by the self-potential method, in Hydrogeological regimes and their subsurface thermal effects, 47, IUGG, Vol. 2, A.E. Beck et al. (Eds), AGU, pp. 151-158.
  6. Lim, S. K., 2006, A Study on the Geothermal Reservoir Modeling using Three-Dimensional SP Simulator, Ph.D. Thesis, Chonbuk University, 132p.
  7. Lim, S. K., Song, Y. H., Lee, T. J., Yasukawa, K., and Song, Y. S., 2007, Three-Dimensional SP Modeling at a Geothermal Site, Geophysics, 7, 164-173.
  8. Lim, S. K., Lee, T. J., Song, Y. H., Song, S. H., Yasukawa, K., Cho, B. W., and Song, Y. S., 2007, Application of SP Monitoring in the Pohang Geothermal Field.
  9. Matsushima, N., Kikuchi, T., Tosha, T., Nakao, S., Yano, Y., and Ishido, T., 2000, Repeat SP measurements at the Sumikawa geothermal field, Japan, Proc. World Geothermal Congress, Kyushu-Tohoku, Japan, pp. 2725-2730.
  10. Morrison, F., Corwin, R. F., De Moully, G., and Durand, D., 1978, Electrical signals generated by the collapse of the pillars of a gypsum quarry, C. R. Acad. Sci., 308, 33-38.
  11. Naudet, V., Revil, A., Rizzo, E., Bottero, J.-Y., and Begassat, P., 2004, Groundwater redox conditions and conductivity in a contaminant plume from geoelectrical investigations, Hydrology and Earth System Sciences, 8(1), 8-22. https://doi.org/10.5194/hess-8-8-2004
  12. Onsager, L., 1931, Reciprocal relations in irreversible processes (1), Physical Review, 37, 405-426. https://doi.org/10.1103/PhysRev.37.405
  13. Perrier, F., Trique, M., Lorne, B., Avouac, J. P., Hautot, S., and Tarits, P., 1999, Electrical variations associated with periodic spring discharge in western Nepal, CR Acad. Sci., Paris, serie II 328, pp. 73-79.
  14. Sasaki, Y., 1994, 3-D resistivity inversion using the finiteelement method, Geophysics, 59, 1839-1848. https://doi.org/10.1190/1.1443571
  15. Sill, W. R., 1983, Self-potential modeling from primary flows, Geophysics, 48, 76-86. https://doi.org/10.1190/1.1441409
  16. Song, S. H., Lee, K. S., Kim, J. H., and Kwon, B. D., 2000, Application of SP and Pole-pole Array Electrical Resistivity Surveys to the Seawater Leakage Problem of the Embankment, Econ. Environ. Geol., 33(5), 417-424.
  17. Song, S. H., and Yong, H. H., 2003, Application of SP monitoring to the analysis of anisotropy of aquifer, Econ. Environ. Geol., 36, 49-58.
  18. Jardani, A., Dupont, J. P., and Revil, A., 2006, Self-potential signals associated with preferential groundwater flow pathways in sinkholes, Journal of Geophysical Research, 111, B09204.
  19. Jouniaux, L., Bernard, M. L., Zamora, M., and Pozzi, J. P., 2000, Streaming potential in volcanic rocks from Mount Pelee, J. Geophys. Res., 105, 8391-8401. https://doi.org/10.1029/1999JB900435
  20. Jouniaux, L., Maineult, A., Naudet, V., Pessel, M., and Sailhac, P., 2009, Review of self-potential methods in hydrogeophysics, Comptes Rendus Geoscience, 341, 928-936. https://doi.org/10.1016/j.crte.2009.08.008
  21. Revil, A., Naudet, V., and Meunier, J. D., 2004, The hydroelectric problem of porous rocks: inversion of the position of the water table from self-potential data, Geophys. J. Int., 159, 435-444. https://doi.org/10.1111/j.1365-246X.2004.02422.x
  22. Yasukawa, K., Mogi, T., Widarto, D., and Ehara, S., 2003, Numerical modeling of a hydrothermal system around Waita volcano, Kyushu, Japan, based on resistivity and self-potential survey results, Geothermics, 32, 21-46. https://doi.org/10.1016/S0375-6505(02)00048-2
  23. Yungul, S. H., 1954, Spontaneous-potential survey of a copper deposit at Sariyer, Turkey, Geophysics, 19, 455-458. https://doi.org/10.1190/1.1438018
  24. Zachos, K., 1963, Discovery of a copper deposit in Chalkidiki Peninsula, northern Greece (in Greek with English summary), Institute of Geology and Subsurface Research Publication, 8, 1-26.