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Study on the Current Horizontal Stress Characteristics of the Tertiary Rock Formations in the Pohang Basin by Integrated Analysis with In-situ Rock Stress Measurement and Borehole Scanning Data Set

현장 초기응력 측정과 시추공 이미지 스캐닝 자료의 통합 분석을 통한 포항분지 제 3기 지층 내 수평응력 분포 특성 연구

  • 배성호 ((주)지오제니컨설턴트) ;
  • 전석원 (서울대학교 공과대학 에너지시스템공학부) ;
  • 김장순 ((주)지오제니컨설턴트) ;
  • 박권규 (한국지질자원연구원 지구환경연구본부)
  • Received : 2016.08.16
  • Accepted : 2016.08.26
  • Published : 2016.08.31

Abstract

In this study, the current horizontal stress characteristics of the Tertiary rock formations in the Pohang Basin are investigated on the basis of the in-situ rock stress measurements at depths from 75 m to 716 m of the 3 test boreholes in the Doumsan area, Pohang. The deep hydraulic fracturing stress measurement results indicated that the horizontal stress components in the test site appear far lower than the average ones by the linear fit for the data set measured from the other domestic sites. But, borehole scanning revealed clearly that lots of small and large scale borehole failures occurred due to the low strength characteristics of the existing rocks. To obtain more accurate and overall information on the horizontal stress direction, the integrated analysis combining the hydraulic fracturing stress measurement and borehole scanning data set were additionally carried out. The analysis results showed that in the upper sedimentary and the lower volcanic rock formation, the dominant orientations of the current maximum horizontal stress components were appeared in the range of $80^{\circ}{\sim}100^{\circ}$ (N80E~N80W) and $120^{\circ}{\sim}140^{\circ}$ (N60W~N40W), respectively. From this study result it was found that the maximum horizontal stress directions have a tendency to rotate in a clockwise direction as the rock formation changes with depth in the test site.

Keywords

In-situ rock stress measurement;Hydraulic fracturing;Pohang Basin;Borehole failures;Maximum horizontal stress direction

Acknowledgement

Grant : 고수압 초장대 해저터널 기술자립을 위한 핵심요소 기술개발

Supported by : 건설교통과학기술진흥원

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