The Journal of Engineering Geology (지질공학)

The Korean Society of Engineering Geology (대한지질공학회)
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Characterization of Area Installing Combined Geothermal Systems : Hydrogeological Properties of Aquifer

복합지열시스템에 대한 부지특성화: 대수층의 수리지질학적 특성

  • Mok, Jong-Koo (Division of Geology and Geophysics, Kangwon National University) ;
  • Park, Yu-Chul (Division of Geology and Geophysics, Kangwon National University) ;
  • Park, Youngyun (Division of Geology and Geophysics, Kangwon National University) ;
  • Kim, Seung-Kyum (Division of Geology and Geophysics, Kangwon National University) ;
  • Oh, Jeong-Seok (Division of Geology and Geophysics, Kangwon National University) ;
  • Seonwoo, Eun-Mi (Division of Geology and Geophysics, Kangwon National University)
  • 목종구 (강원대학교 지질지구물리학부) ;
  • 박유철 (강원대학교 지질지구물리학부) ;
  • 박영윤 (강원대학교 지질지구물리학부) ;
  • 김승겸 (강원대학교 지질지구물리학부) ;
  • 오정석 (강원대학교 지질지구물리학부) ;
  • 선우은미 (강원대학교 지질지구물리학부)
  • Received : 2017.08.23
  • Accepted : 2017.09.20
  • Published : 2017.09.30
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Abstract

This study was performed in order to hydrogeological analysis of aquifer, which is a necessary part for evaluating the efficiency of the combined well and open-closed loops geothermal (CWG) systems. CWG systems have been proposed for the effective utilization of geothermal energy by combining open loop geothermal systems and closed loop geothermal systems. Small aperture CWG systems and large aperture CWG systems were installed at a green house land with water curtain facilities in Chungju City. Aquifer tests include pumping tests and step-drawdown tests were conducted to analyse hydrogeological characteristics of aquifer in the study area. The transmissivity was estimated in the range of $13.49{\sim}58.99cm^2/sec$, and the storativity was estimated in the range of $1.13{\times}10^{-5}{\sim}5.20{\times}10^{-3}$. The geochemical analysis showed $Ca^{2+}$ ion and ${HCO_3}^-$ ion were dominant in groundwater. The Langelier Saturation Index and the Ryznar Stability Index showed low scaling potential of groundwater. In the analysis of vertical water temperature change, the geothermal gradient was estimated as $2.1^{\circ}C/100m$, which indicated the aquifer was enough for geothermal systems. In conclusion, groundwater is rich, can stably use geothermal heat, and it is less likely to cause deterioration of thermal energy efficiency by precipitation of carbonate minerals in study area. Therefore, the study area is suitable for installation of the combined geothermal system.

본 연구는 복합지열시스템의 효율성 평가를 위하여 필요한 부분인 대수층의 수리지질학적 분석을 위하여 수행되었다. 복합지열시스템은 개방형 지열시스템과 밀폐형 지열시스템을 결합하여 지열의 효과적 이용을 목적으로 제안되었으며, 연구지역인 충주시 금가면의 수막재배 지역에 소구경 복합지열시스템과 대구경 복합지열시스템이 설치되었다. 연구 지역 대수층의 수리지질학적 특성 분석을 위하여 양수시험과 단계양수시험을 포함하는 현장수리시험 결과, 대수층의 투수량계수는 $13.49{\sim}58.99cm^2/sec$의 범위를 가지며, 저유계수는 $1.13{\times}10^{-5}{\sim}5.20{\times}10^{-3}$의 범위로 분석되었다. 또한, 지구화학적 분석에서 지하수 성분 중 $Ca^{2+}$이온과 ${HCO_3}^-$ 이온이 우세한 것으로 나타났고, 랑겔리어 지수 및 리즈나 지수 분석에서 지하수 내의 탄산염 광물의 침전 가능성이 낮게 평가되었다. 수직적 수온 변화 분석에서는 평균 증온률이 $2.1^{\circ}C/100m$로 평가되어 지열 특성이 충분한 것으로 나타났다. 따라서, 연구지역에서는 지하수의 양이 풍부하고 지중열을 안정하게 사용할 수 있으며 탄산염 광물의 침전에 의한 열에너지 효율 저하가 발생할 가능성이 낮으므로 복합지열시스템 설치가 적합한 것으로 판단된다.

Keywords

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