【摘要】 钻杆式水压致裂原地应力测试系统的柔性严重影响最大水平主应力的计算精度,如何提高深孔水压致裂测试精度是这一领域的热点和难点。为准确确定河北易县紫荆关断裂附近孔深达600 m的ZJGTEST-ZK 10钻孔原地应力状态,采用现场测试曲线和室内抗拉强度试验共同对研究区最大水平主应力量值进行比选确定。利用钻孔所揭露岩芯开展巴西圆盘劈裂、空心岩柱液压致裂以及双圆环直接拉伸3种室内试验确定该区域花岗岩的抗拉强度,测定值范围为6.42～9.35 MPa。现场水压致裂测试抗拉强度均值为8.01 MPa,与室内试验结果具有可比性。研究结果确定了该区最大水平主应力为17.70～35.38 MPa,最小水平主应力为10.36～19.38 MPa,垂直主应力为5.82～15.49MPa,地应力状态有利于逆断层活动,应力场状态稳定且最大水平主应力方向为北东向,范围为NE40°～56°。通过测试结果的对比分析,当测试段深度大于440 m时,测试系统柔性的影响作用明显,基于室内试验测定岩石抗拉强度而计算的最大水平主应力量值明显大于基于重张压力计算值,且更能反映区域真实地应力状态。更多还原

【Abstract】 The compliance of a drilling-rod hydraulic fracturing test system has severe impacts on the calculation precision of the maximum horizontal principal stresses. How to improve the accuracy of deep hole hydraulic fracturing test has always been a hot topic and tough task in this field. In order to determine the in-situ stress state in a borehole of ZJGTEST-ZK 10 of 600 m deep,close to the Zijingguan fault in the Yi County,Hebei Province,Brazilian disk tests,hollow cylinder hydro-fracturing test,and concentric annular core tension test were conducted so as to determine the tensile strength of rock cores,and the tensile strength of granite cores ranges from 6.42 MPa to 9.35 MPa. The average tensile strength determined by the in-situ hydraulic fracturing test was 8.01 MPa,which was consistent with those determined by the above three laboratory tests. Based on the ten successful in-situ hydraulic fracturing tests and three laboratory tests,final determined maximum horizontal principal stresses range from 17.70 MPa to 35.38 MPa,the measured minimum horizontal principal stresses range from 10.36 MPa to 19.38 MPa,and the estimated vertical principal stresses range from 5.82 MPa to 15.49 MPa,the orientation of the maximum horizontal principal stress is NE,and ranges from NE40° to NE56°. The stress state is stable,and favorable for thrust faulting. By comparing the maximum horizontal principal stress magnitudes based on different tensile strengths and reopening pressures,the maximum horizontal principal stresses based on tensile strengths are markedly greater than those based on reopening pressures due to the negative impacts from the test system compliance when the test interval is deeper than 440 m. For the deeper test intervals,the maximum horizontal principal stresses based on tensile strengths indicate true in-situ stress state.更多还原