Accurately determining the stress state in deep shale reservoirs is the key to the efficient development of shale gas and other unconventional energy sources. An effective method to increase the evaluation and calculation accuracy of in-situ stress parameters in a deep shale reservoir is to combine different methods to obtain different stress information, such as obtaining the minimum horizontal principal stress based on the in-situ stress measurement, predicting the magnitudes of horizontal stress difference and the horizontal principal stresses by establishing the stress profile based on the rheological model, and estimating the direction of the maximum horizontal principal stress by the wellbore failure imaging logging. We applied this research idea to Well SZ1 in Hanzhong, Shaanxi Province. The minimum horizontal principal stress obtained by hydraulic fracturing ranged from 32 to 41 MPa; Then, the variation laws of rock rheological parameters with the depth were determined by the rock mechanical parameters obtained from cross-dipole acoustic logging data. And combined with the burial history of the reservoir and the strain rate of the crust, the stress profile of Well SZ1 was established. The results show that the magnitude of horizontal stress difference in the depth range of 1950~2025 m in the Niutitang Formation is between 10~15 MPa, and ranges of the minimum and maximum principal stresses are 28~41 MPa and 47~49 MPa, respectively. The predicted horizontal minimum principal stress values are in good agreement with the measured results. Based on the in situ stress measurement and predicted stress profiles, Well SZ1 is characterized by normal faulting (Sv > SH > Sh)or a combination of normal and strike-slip faulting regimes (Sv≈SH > Sh).The horizontal stress difference decreases with the increase of the gamma value, indicating that the stress profile has a good corresponding relationship with the formation lithology. Based on the distribution characteristics of borehole-induced tensile fractures recorded by imaging logging, the direction of the maximum horizontal principal stress in Well SZ1 is ~N74°W, which is consistent with the direction of the regional tectonic stress field. This study provides an important basis for accurately understanding the in-situ stress state of the target layer of Well SZ1, as well as the later horizontal well layout and fracturing control.

In order to more scientifically guide the site selection of CNNC nuclear technology industrial park,it is necessary to analyze the in situ stress state and the distribution law of the rock mass within the scope of the project area of the preselected site.Therefore,in-situ stress measurement was carried out by hydraulic fracturing in two 450 mdrilling in the project area,and 4 methods were used in the data processing stage to determine the instantaneous shut-in pressure to make sure the principal stress value reliable and accurate.The hydro-fracturing test results indicate that the maximum horizontal principal stress value is 6.66 ～ 25.91 MPa and the minimum is 3.94 ～ 15.76 MPa.The stress regime is SH ＞ Sh ＞ Sv,showing that the stress filed is dominated by the tectonic horizontal stress,and this kind of stress state is beneficial to reverse fault activities.The fracture impression test results show that the orientation of the principal horizontal stress in the project area is dominantly in the NE direction,which is in general agreement with that of regional tectonic stress field.Based on the measured data,the stress state parameters Kay,KHv,KHh,μm and τm were calculated,and the fault activity of the preselected site was analyzed using Coulomb friction sliding criterion,so as to synthetically evaluate the impact of the stress field characteristicsof the preselected site on the stability of rock mass engineering.

Hydraulic fracturing and piezomagnetic overcoring in-situ stress measurements were carried out in two boreholes in the southwestern Longmenshan Fault Zone to understand the current in-situ stress state and stress change after the Lushan Ms 7.0 earthquake on the April 20th,2013.Measurement results show that the maximum horizontal principal stress and minimum horizontal principal stress at the Qiaoqi borehole is 19.60～25.83 MPa and 10.47～18.47 MPa within the depth of 128～188 m,with an orientation of N63°～85°W;the maximum horizontal principal stress and minimum horizontal principal stress at the Tianquan borehole is 8.21 ～ 9.31 MPa and 5.20 ～ 7.73 MPa within the depth range of 114 ～ 142m,with an orientation of N59°W.Relationships between horizontal stress and vertical stress of the two measuring points are σH＞σh＞σv.The average ratios of maximum and minimum horizontal stress to vertical stress at the Qiaoqi borehole are 5.27 and 3.01 respectively.The average ratios of maximum and minimum horizontal stress to vertical stress at the Tianquan borehole are 2.60 and 1.76 respectively.The results that horizontal stress is higher than vertical stress will lead to a reverse fault activity.Comparison of insite stress states in this area before and after the Lushan earthquake suggests that after the earthquake the accumulation of stress of the unbroken active faults on both sides of the epicenter has been increasing.What's more,the stress magnitude at the Qiaoqi borehole improves significantly after the earthquake,which is in consistent with the monitoring results at the Qiaoqi.On the basis of in-situ stress data and Coulomb faulting criterion,the maximum horizontal principal stress at Qiaoqi was between the minimum and the maximum of fault slip before the earthquake,and exceeded the maximum after the earthquake.The maximum horizontal principal stress at Feixianguan was lower than the maximum of fault slip before earthquake.μm,the ratio between the maximum horizontal principal stress [(σ1-σ3)/2] and average stress [(σ1+σ3)/2],can be used to evaluate the present stress accumulation level and the seismic risk.The pre-earthquake μm value at Qiaoqi was 0.16～0.72,with an average of 0.50,and the post-earthquake μm value at Qiaoqi is 0.71 ～ 0.81,with an average value of 0.77.The pre-earthquake μm value at Feixianguan was 0.31～0.35,with an average of 0.32,and the post-earthquake μm value at Tianquan was 0.53～0.57,with an average value of 0.55.μmvalues in two study areas show a big difference.This study concludes that the stress in the northern and southern segments of the Longshan fault zone has been accumulated,which can increase possibility of fault slipping,especially in the northern segment.

台湾海峡西岸地区受到欧亚板块、太平洋板块和菲律宾板块的共同作用,具有复杂的应力场特征,但本地区现阶段地壳应力状态研究程度较低.为深入了解本区地应力特征,本文采用水压致裂法在福建平潭和广东饶平钻孔中进行了地应力测量,并结合其他实测及震源机制解资料,讨论了台湾海峡西岸构造应力场特征.结果显示平潭和饶平钻孔地应力优势作用方位分别为N19°W和N37°W;由震源机制解资料得到的研究区应力场方向表现为从北向南由NNW方向转向EW方向的扇形分布.地应力状态的水平变化趋势,大致以沙县—南日岛断裂为界,北部为低应力区,南部为高应力区,且南部大致以九龙江下游断裂附近开始,呈现由北向南,地应力水平逐渐降低的趋势.在研究区北部、中部、南部分别选取平潭、泉州、饶平三个钻孔,利用库伦准则对断层活动性进行判断,认为海峡西岸北部地区应力水平较低,断层活动性较弱;泉州所在的海峡西岸中部地区应力已积累到较高的水平,断层失稳滑动的可能性比较大;饶平邻近区域在近期断层失稳滑动的可能性不高.

<正>通过布设一条穿过澜沧、宁洱和通海3个历史地震活跃区的长546 km的罗平—孟连大地电磁测深(MT)剖面,观测得到了可靠的野外资料,采用先进的资料处理和分析技术,获得区域的定性结构和区域构造走向等信息,在此基础上,开展二维反演,得到沿剖面的二维地壳及上地幔介质电导率的结构模型。