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2007 Vol.44, Issue 1 Preview Page
Three-Dimensional SP Modeling at a Geothermal Reservoir Site

지열 저류층에서의 3차원 SP 모델링

임성근, 송윤호, 이태종, Kasumi Yasukawa, 송영수

Sung Keun Lim, Yoonho Song, Tae Jong Lee, Kasumi Yasukawa and Young Soo Song

28 February 2007. pp. 9-19
PDF Citation
Abstract
Three-dimensional (3-D) self-potential (SP) simulation algorithm (3-D SP simulator) has been developed by combining the geothermal simulator PT (Pressure and Temperature) and the 3-D resistivity modeling algorithm and applied to the field SP data measured from the Pohang geothermal site. Developed 3-D SP simulator calculates 3-D SP distributions from the fluid velocity and temperature distributions, which can be earned by solving the mass and energy balance equations. The electrokinetic cross-coupled current sources are calculated from a velocity distribution instead of a pressure gradient, which results in more realistic flow models than those based on the temperature variations. The algorithm was successfully verified by comparison with an analytic solution for injection model in a homogeneous half space. To get a basic insight for application of the 3-D modeling algorithm, modeling with a simplified model for the Pohang geothermal field was performed in its natural state. The possible range of cross-coupling coefficient and permeability distribution for each layer in the Pohang site could be determined by trial and error method, because we have no information about hydraulic conductivity of each layer. Resistivity distribution for the model, however, was given based on the results of 3-D magnetotelluric interpretation. After the simplified Pohang model in natural state was obtained, we calculated the SP responses caused by the perturbations of geothermal reservoir according to the well pumping and injection. The results show that the SP value calculated from the Pohang geothermal model is similar to the field SP monitoring data during the well pumping.
Keywords
SP
Geothermal
Simulation
Cross-coupling coefficient
Permeability
이 연구에서는 유체와 열 흐름에 의한 자연전위(self-potential, SP)를 3차원 지하 구조와 관련해서 정량적으로 연구하기 위하여 Bodvarsson (1982)에 의해서 개발된 지열 시스템 시뮬레이션 알고리즘인 PT 모듈(Pressure and Temperature module)과 박권규(1994)에 의한 전위계산 모듈을 결합하여 3차원 SP 시뮬레이션 알고리즘을 구성하였다. 전기역학적인 흐름에 의한 전류원이 압력이 아닌 유체 속도로부터 구해지므로, 온도 분포에 기초하여 더욱 현실적인 유체 흐름을 가진 모델을 구할 수 있다. 균질한 반무한 공간 내에 유체 주입 모델에 대한 해석적인 해와 개발된 알고리즘에 의한 결과가 거의 일치하여, 본 연구에서 개발된 알고리즘의 타당성을 확인할 수 있었다.　　이 연구의 3차원 SP 모델링 알고리즘을 포항 지열 개발 지역에 적용하고자, 포항 지열 지역의 단순화된 모델을 구성하고 현장에서 구한 다양한 지구물리 자료를 함께 이용하여 자연 상태 모델링을 수행하였다. 포항 지열 현장 모델에서 층서 구조의 수리 전도도를 구할 수 없기 때문에, 속도-전류 상호결합계수 및 투수율 분포는 각 층의 암석 특성을 토대로 시행착오법으로 결정하였다. 하지만 전기비저항 분포는 3차원 MT 탐사의 해석 결과를 이용하였다. 자연 상태 모델을 구한 후에 지열수 양수 및 주입에 의한 시간에 따른 SP 모델 반응을 계산하였다. 그 결과 실제 현장에서 양수 시험 동안에 수행된 SP 모니터링 자료와 비슷한 SP 반응 값을 구할 수 있었다.
키워드
자연전위
지열
시뮬레이션
상호결합계수
투수율
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Information
  • Publisher :The Korean Society of Mineral and Energy Resources Engineers
  • Publisher(Ko) :한국자원공학회
  • Journal Title :Journal of the Korean Society for Geosystem Engineering
  • Journal Title(Ko) :한국지구시스템공학회지
  • Volume : 44
  • No :1
  • Pages :9-19
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