In-situ stress measurement and its significance within the depth of 3 ~ 4 km in Tangshan area.SHANGGUAN Shuantong1, SUNDongsheng2,ZHANG Guobin1,CHEN Dongfang2,3, QIXiaofei1, YANG Yuehui2,3, QIAOYongchao1 ,LI A-wei2
Abstract:The magnitude and direction of in-situ stress are important parameters in the deployment of injection production well pattern, the design of hydraulic fracturing simulation and the evaluation of induced earthquakes. In this paper, the Anelastic Strain Recovery (ASR in short) in-situ stress measurement method was employed to obtain the in-situ stress state of 3 ~ 4 km depth of of dry hot rock in Matouying area, Laoting County, Tangshan City. The results show that: (1) the magnitude of in-situ stress increases with depth. within the range of 3 139 ~ 3 934 m depth, the minimum horizontal principal stress is 59.0 ~ 90.7 MPa, the maximum horizontal principal stress is 103.7 ~ 123.6 MPa, and the maximum horizontal principal stress direction is N83 ~ 114°E. (2) the relationship of three principal stresses is σH > σv > σh, which indicates that the tectonic stress field gives priority to the horizontal stress, and the stress state is favorable for activity of strike-slip faults. (3) The stability of the fault was studied according to Mohr-Coulomb criterion, the result shows that the ratios of shear to effective normal stress are lower than those Byerlee’s law, indicating that the faults are in the relatively stable stress environment near the well M1 in matouying area within 3~4 km depth. (4) The analysis of the relationship between the water injection development and fault stability shows that the faults may become instability near the injecting well, when the continuous injection pressure on the ground reaches or exceeds about 28 MPa during the water injection development of 3900-4000 m depth in the study area, leading to the occurrence of medium and small earthquakes, which should be prevented in the development and utilization of the dry hot rock. This study have certain reference value for the analysis of geodynamics and the development and utilization of dry and hot rocks in Tangshan area.