In-situ Stress and Fault Reactivation Potential Analysis in Ilan Sanshing and Chingshui Area

• Main Authors: Yu-hsuan Chiang, 江俞萱
• Other Authors: Jih-hao Hung
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/87922342786784672237

碩士 === 國立中央大學 === 地球科學學系 === 103 === The aim of this study is to analyze the possibility of the fault reactivation in Sansing Area of Ilan. The scenario assumes the possible fluid injection activitis for Enhanced Geothermal System (EGS), which may generate high fluid pressure and trigger slip along fault planes. We determined the in-situ stress states with core logging data from the HongChaiLin(HCL) and IC21 wells,. We estimated the pore pressures from the hydrostatic pressure gradient (10.37MPa/km). The vertical stresses (SV) were calculated from core density logs of the HCL well. The gradient of the vertical stress is 21.63MPa/km. The minimum horizontal stress (Shmin) is measured with hydraulic fracture test, and its gradient is 18.01MPa/km. The maximum horizontal stress (SHmax) is estimated with stress polygon method, and its upper bound is estimated using Anderson faulting theory. The upper bound gradient of SHmax is 34.20 MPa/km. The orientation of the maximum horizontal stress is 30° from the Caliper logs of IC21 well. We also construct the 3-D geological structure model of Sansing and Chigshui area, and using the model for assessing the risk of fault reactivation with 3DStress and Traptester softwares. Under current in-situ stress state, Zhuosui fault has higher slip tendency than other faults. We also concluded that the Zhuosui fault has higher dilation tendency than others from the dialation analysis. In addition, The sensitivity analysis shows that the minimum horizontal stress is the main factor influence on the critical pressure perturbation (Pcp). The scenarios tests of fluid injection upon the Zhuosui fault show that the critical pressure perturbation allowed is 2.566MPa, assuming the normal faulting stress regime, and the critical pressure perturbation is 2.417MPa for strike-slip faulting stress states.