Characterization of Area Installing Combined Geothermal Systems : Hydrogeological Properties of Aquifer

Jong-Koo Mok; Yu-Chul Park; Youngyun Park; Seung-Kyum Kim; Jeong-Seok Oh; Eun-Mi Seonwoo

doi:10.9720/kseg.2017.3.293

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2017 Vol.27, Issue 3 Preview Page Next Page

Research Article

Characterization of Area Installing Combined Geothermal Systems : Hydrogeological Properties of Aquifer 복합지열시스템에 대한 부지특성화: 대수층의 수리지질학적 특성

September 2017. pp. 293-304

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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 13.49~58.99 cm²/sec, and the storativity was estimated in the range of 1.13 × 10⁻⁵~5.20 × 10⁻³. The geochemical analysis showed Ca²⁺ ion and HCO₃⁻ 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^oC/100 m, 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.

Keywords

CWG systems

hydrogeological analysis

aquifer tests

scaling potential

geothermal gradient

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 13.49~58.99 cm²/sec의 범위를 가지며, 저유계수는 1.13 × 10⁻⁵~5.20 × 10⁻³의 범위로 분석되었다. 또한, 지구화학적 분석에서 지하수 성분 중 Ca²⁺이온과 HCO₃⁻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^oC/100 m로 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.

키워드

복합지열시스템

수리지질학적 분석

수리시험

탄산염 침전

증온률

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Information

Publisher :Korean Society of Engineering Geology
Publisher(Ko) :대한지질공학회
Journal Title :The Journal of Engineering Geology
Journal Title(Ko) :지질공학
Volume : 27
No :3
Pages :293-304
Received Date : 2017-08-23
Revised Date : 2017-09-18
Accepted Date : 2017-09-20
DOI :https://doi.org/10.9720/kseg.2017.3.293

The Journal of Engineering Geology ISSN:1226-5268(Print) 2287-7169(Online) 지질공학

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