HYDRAULIC FRACTURING STRESS MEASUREMENTS IN XUEFENGSHAN DEEP BOREHOLE AND ITS SIGNIFICANCE
CHEN Qunce;SUN Dongsheng;CUI Jianjun;QIN Xianghui;ZHANG Chongyuan;MENG Wen;LI Awei;YANG Yuehui;Institute of Geomechanics,Chinese Academy of Geological Sciences;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources;School of Engineering and Technology,China University of Geosciences (Beijing);
By use of the recently developed hydraulic fracturing in situ stress measurement system,valid data of 16 depth intervals at the borehole depth range of 170 ～ 2021 m in the Xuefengshan deep borehole were obtained,which are the first reported results obtained at the borehole depth deeper than 2000 m in China. The test results showed that the magnitude of the in situ stress increased with the depth of the borehole. By linear regression,the relationship of the maximum and minimum horizontal principal stresses with the depth of the test borehole respectively are S_H= 0. 03328 H + 5. 25408, and S_h= 0. 0203 H +4. 5662, and at the borehole depth of 2021 m,the magnitude of which are 66. 31 MPa and 43. 33 MPa respectively. Based on the hydraulic fracturing test data, combined with the BHTV and borehole temperature logging test results,the analysis on the stress state of the study area were carried out. In the range of 170 ～ 800 m borehole depth,the relationship of the three principal stresses are S_HS_hS_v,which are favourable for reverse faulting; In the range of 1000 ～ 2021 m borehole depth,the relationship changes to S_HS_vS_h,which implied that the deep stress regime of this area are strike-slip faulting. The direction of the maximum horizontal principal stress is in NW ～ NWW direction. According to Mohr-Coulomb criterion,the activity of the faults of the study area were discussed and the conclusion were obtained that the faults of this area are in stable state.