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The Stability Assessment of an Aquifer in Pohang Yeongil Bay due to CO2 Injection

이산화탄소 주입에 따른 포항 영일만 대수층 안정성평가

  • Kim, Nam-Hoon (Department of Energy Systems Engineering, Seoul National University) ;
  • Jung, Hyung-Sik (Department of Energy Systems Engineering, Seoul National University) ;
  • Kim, Gvan-Dek (Department of Energy Systems Engineering, Seoul National University) ;
  • Jeong, Hoonyoung (Department of Energy Resources Engineering, Seoul National University) ;
  • Shin, Hyundon (Department of Energy Resources Engineering, Inha University) ;
  • Kwon, Yi-Kyun (Department of Geoenvironmental Sciences, Kongju National University) ;
  • Choe, Jonggeun (Department of Energy Resources Engineering, Seoul National University)
  • 김남훈 (서울대학교 에너지시스템공학부) ;
  • 정형식 (서울대학교 에너지시스템공학부) ;
  • 김관덕 (서울대학교 에너지시스템공학부) ;
  • 정훈영 (서울대학교 에너지자원공학과) ;
  • 신현돈 (인하대학교 에너지자원공학과) ;
  • 권이균 (공주대학교 지질환경과학과) ;
  • 최종근 (서울대학교 에너지자원공학과)
  • Received : 2018.05.11
  • Accepted : 2018.06.20
  • Published : 2018.06.30

Abstract

It is imperative to inject carbon dioxide($CO_2$) into an aquifer for alleviating the emission of $CO_2$. However, faults in the aquifer can be reactivated due to pressure increasement. Analyses of pressure change of the aquifer is necessary to prevent the fault reactivation. In this research, we assess the stability of an aquifer in Pohang Yeongil bay by investigating the pressure variation of faults EF1 and EF2. Two scenarios, which repeat $CO_2$ injection and suspension during two years, are simulated. Each scenario includes cases of injection rates of 20, 40, and 100 tons/day. In addition, we analyze planned and predicted injection rates for each case. In case of 20 tons/day, the maximum pressure of faults is 65% of the reactivation pressure. Even if daily injection rates are increased to 40 and 100 tons/day, the maximum pressures are 71% and 80% of the reactivation pressures, respectively. For 20 and 40 tons/day cases, planned injection rates almost accord with predicted injection rates during whole simulation period. On the other hand, predicted injection rates are smaller than planned injection rates for the 100 tons/day case due to bottom-hole pressure limit of the injection well.

대수층에 이산화탄소를 주입하여 저장하는 것은 대기 중 이산화탄소 농도를 저감하는데 중요한 역할을 한다. 하지만 이산화탄소 주입 시 대수층의 압력증가로 단층 재활성화가 발생할 수 있다. 이러한 문제를 예방하기위해 이산화탄소 주입에 따른 대수층 압력변화를 분석하는 것이 필요하다. 본 연구에서는 포항영일만 지질모델의 이산화탄소 주입정에서 450 m 떨어진 EF1 단층과 530 m 떨어진 EF2 단층에 대해 안정성 분석을 수행하였다. 약 2년 동안 이산화탄소의 주입과 중단을 반복하는 두 가지 시나리오에서 대수층 압력변화가 단층에 영향을 주는지 일일주입량(20 tons, 40 tons, 100 tons)에 따라 분석하였다. 또한 각 일일주입량 별로 계획 주입량과 예측 주입량을 비교하였다. 이산화탄소 일일주입량이 20 tons인 경우 단층에서의 최대압력이 단충 재활성압의 65% 수준으로 단층의 재활성화 가능성이 낮았다. 일일주입량이 40 tons과 100 tons으로 증가해도 단층에서의 최대 압력이 단층 재활성압의 각각 71%와 80% 정도이다. 또한 일일주입량이 20 tons인 경우와 40 tons인 경우 계획 주입량과 예측 주입량이 거의 일치하였지만 100 tons인 경우 주입정의 공저압력 허용한계로 인해 시뮬레이션 예측 주입량이 계획 주입량에 미치지 못하였다.

Keywords

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