受区域挤压、岩性和构造形态等多种因素的综合影响,复杂构造区具有地应力非均质性和各向异性强、现今地应力场在空间变化大的特征,严重制约了该类地区油气勘探开发进展。为解决复杂构造区地质力学建模难度大、精度低,且现有三维地应力建模方法在复杂构造连片建模中的不准确问题,以库车坳陷博孜大北地区为例,提出了复杂构造区地质体全层系逆向有限元地质力学建模方法,通过对部分起伏较大、跨度大的长条连体背斜迭代扫描,准确建立断层与岩体复杂交切关系,实现了复杂构造区地应力网格建模和误差追溯。明确了博孜大北地区现今地应力分布特征,揭示了博孜大北地区深层储层地应力强非均质性和强各向异性的主控因素,进而通过逆向有限元建模方法明确了钻井过程中产生应力扰动范围。研究结果表明:(1)逆向有限元地质力学建模法是复杂构造区全层系地质力学建模的有效方法,建模结果与实际的勘探开发生产需要吻合度高;(2)明确了盐上岩石力学层结构和浅部高陡地层产状是影响博孜大北地区储层地应力强非均质性和各向异性的关键;(3)逆向有限元地质力学建模法是明确钻井过程中应力扰动范围的有效方法,是保障油气高效勘探开发的重要手段。

Areas with complex geological features have poorly defined geostress distribution patterns with strong geostress heterogeneity and anisotropy, which seriously restrict the progress of oil and gas exploration and development. To solve the problems of high modeling accuracy requirements for complex structures and lithology and inaccuracies in current 3D geomechanical modeling techniques for complex structures, this paper, taking the Bozi-Dabei area in Kuqa depression as an example, proposes a full-stratum inverse finite element geomechanical modeling technique for complex structure areas. By iterative scanning of long and large-scale strip-connected anticlines, the modeling accuracy is improved, and the complex intersection relationship between faults and rock masses is accurately established—thus, the modeling of geostress mesh and error tracing in areas with complex structures is achieved. Using this technique, the current distribution characteristics of geostresses in Bozi-Dabei were clarified, and the main controlling factors of strong geostress heterogeneity and anisotropy in deep reservoirs were revealed. Furthermore, the range of stress disturbance during drilling was clearly defined. Results showed that (1) the modeling technique was effective for full-stratum modeling of complex deformation areas, with high accuracy meeting the needs of exploration, development, and production. (2) The key factors affecting the strong geostress heterogeneity and anisotropy in reservoirs of the study area were the mechanical-layer structure of salt layers and the attitude of shallow high, steep strata. (3) The modeling technique was effective for determining the range of stress disturbance during drilling, thus it can be an important evaluation tool for efficient oil and gas exploration and development.