超深层逆冲推覆构造致密砂岩储层地应力场扰动特征——以塔里木盆地博孜—大北地区白垩系储层为例

Disturbance characteristics of in-situ stress field within ultra-deep tight sandstone reservoirs in thrust-nappe structures: a case study from Cretaceous reservoirs in Bozi-Dabei area, Tarim Basin

张家维 李瑞雪 邓虎成 邢梓萌 张辉 何建华 王志民 杨宇勇 宿航

ZHANG Jiawei LI Ruixue DENG Hucheng XING Zimeng ZHANG Hui HE Jianhua WANG Zhimin YANG Yuyong SU Hang

1. 成都理工大学 能源学院(页岩气现代产业学院), 成都 610059; 2. 油气藏地质及开发工程全国重点实验室(成都理工大学), 成都 610059; 3. 中国石油 塔里木油田分公司 勘探开发研究院, 新疆 库尔勒 841000

1. College of Energy (College of Modern Shale Gas Industry), Chengdu University of Technology, Chengdu, Sichuan 610059, China; 2. National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology), Chengdu, Sichuan 610059, China; 3. Exploration and Development Research Institute, Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China

塔里木盆地库车坳陷博孜—大北地区白垩系致密砂岩储层在由北向南的逆冲推覆下，发育了一系列大规模的北倾断层和叠瓦状堆叠的褶皱构造。复杂的构造形貌致使该区地应力复杂多变，储层改造效果差异明显。因此，亟需厘清研究区内复杂构造对地应力的扰动特征。结合多种方法对单井现今地应力的精确解释，分别分析断裂、褶皱和断褶复合构造对地应力的扰动效果，明确了相关扰动机理，并绘制了研究区地应力扰动特征分区图。基于扰动特征，绘制了不同构造的地应力扰动特征模式图，并提出井位、井轨迹建议。断裂对地应力有卸载作用，断裂附近水平主应力梯度出现不同程度的降低，其中最大水平主应力梯度降低约0.3 MPa/hm；近EW走向的断裂使得近SN向的区域应力方向发生顺时针偏转，偏转角度最大达60°；不同规模断裂的扰动范围为断距的60%。当地层曲率超过0.4 km-1时，褶皱对地应力存在扰动，褶皱地层上部张性扰动区地应力较区域应力减小，下部挤压扰动区地应力增加；张性扰动区最大水平主应力梯度最大约降低0.3 MPa/hm，地应力方向逆时针偏转，偏转角度最大达70°；褶皱变形曲率越大，张性扰动区厚度越大，扰动越明显。断褶复合构造下，断裂扰动区和褶皱张性扰动区叠加会使得地应力进一步减小，地应力方向在两者扰动效果抵消后较区域应力偏转较小或不偏转。综合考虑储层改造难易程度和致密气富集特征，应优先于断褶复合构造带断裂和褶皱张性扰动叠合区部署钻井，建议钻深不超过褶皱中性面，水平井轨迹沿EW向设计。

A series of large-scale north-dipping faults and imbricate folding structures have developed in the Cretaceous ultra-deep tight sandstone reservoirs in Bozi-Dabei area of Kuqa Depression of Tarim Basin under the north-to-south thrust-nappe movement in this area. This complex structural morphology results in highly variable in-situ stress fields, leading to significant differences in reservoir modification effectiveness. Therefore, it is urgent to clarify the disturbance characteristics of the in-situ stress caused by the complex structures in the study area. In this study, multiple methods were combined for the accurate interpretation of the current in-situ stress of a single well. The disturbance effects of faults, folds, and fault-fold composite structures on the in-situ stress were analyzed separately. The relevant disturbance mechanisms were identified, and a zoning map of the disturbance characte-ristics of the in-situ stress for the study area was presented. Based on these disturbance characteristics, models of in-situ stress disturbance for different structures, as well as recommendations for well deployment and trajectory, were proposed. Faults exhibit an unloading effect on the in-situ stress, leading to varying degrees of reduction in the horizontal principal stress gradient near the faults, with the maximum reduced by about 0.3 MPa/hm. Near EW-oriented faults, the regional stress direction near SN exhibits a clockwise deflection, with the maximum deflection angle reaching 60°. The disturbance range of faults with different scales is approximately 60% of the fault throw. A disturbance of the in-situ stress appears when the strata curvature exceeds 0.4 km-1. The in-situ stress is lower than the regional stress in the upper tensile disturbance zone of the folded strata, while it increases in the lower compressive disturbance zone. In the tensile disturbance zone, the maximum decrease in the horizontal principal stress gradient is approximately 0.3 MPa/hm, with the stress direction deflecting counterclockwise, reaching a maximum deflection angle of 70°. The greater the fold deformation curvature, the thicker the tensile disturbance zone, and the more significant the disturbance. Under fault-fold composite structures, the superposition of fault disturbance zones and fold tensile disturbance zones further reduces the magnitude of the in-situ stress. After offsetting the disturbance effects of both, the in-situ stress direction deviates less or does not deviate at all from the regional stress. Considering the difficulty of reservoir modification and the characteristics of tight gas enrichment, drilling should be prioritized in the overlapping areas of faults and fold tensile disturbance zones within the fault-fold composite structure zone. It is recommended that the drilling depth should not exceed the neutral plane of the folds, and the horizontal well trajectory should be designed along the EW direction.

国家自然科学基金面上项目(42072182)和四川省杰出青年科技人才项目(2020JDJQ0058)联合资助。

https://doi.org/10.11781/sysydz202404760