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Development of Efficient Monitoring Algorithm at EGS Site by Using Microseismic Data

미소진동 자료를 이용한 EGS 사이트에서의 효율적인 모니터링 알고리듬 개발

  • Lee, Sangmin (Dept. of Earth Resources and Environmental Engineering, Hanyang Univ.) ;
  • Byun, Joongmoo (Dept. of Earth Resources and Environmental Engineering, Hanyang Univ.)
  • 이상민 (한양대학교 자원환경공학과) ;
  • 변중무 (한양대학교 자원환경공학과)
  • Received : 2016.07.05
  • Accepted : 2016.08.16
  • Published : 2016.08.31

Abstract

In order to enhance the connectivity of fracture network as fluid path in enhanced/engineered geothermal system (EGS), the exact locating of hydraulic fractured zone is very important. Hydraulic fractures can be tracked by locating of microseismic events which are occurred during hydraulic fracture stimulation at each stage. However, since the subsurface velocity is changed due to hydraulic fracturing at each stage, in order to find out the exact location of microseismic events, we have to consider the velocity change due to hydraulic fracturing at previous stage when we perform the mapping of microseimic events at the next stage. In this study, we have modified 3D locating algorithm of microseismic data which was developed by Kim et al. (2015) and have developed 3D velocity update algorithm using occurred microseismic data. Eikonal equation which can efficiently calculate traveltime for complex velocity model at anywhere without shadow zone is used as forward engine in our inversion. Computational cost is dramatically reduced by using Fresnel volume approach to construct Jacobian matrix in velocity inversion. Through the numerical test which simulates the geothermal survey geometry, we demonstrated that the initial velocity model was updated by using microseismic data. In addition, we confirmed that relocation results of microseismic events by using updated velocity model became closer to true locations.

Acknowledgement

Supported by : 한국에너지기술평가원(KETEP)

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