姬塬地区延长组长8储层现今地应力特征及其影响因素
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摘要: 鄂尔多斯盆地姬塬地区延长组长8储层致密油资源丰富，现今地应力场量化表征分析是保障效益开发的关键内容。本次研究借助成像测井解译、地应力实验测试和常规测井计算等方法手段，对长8储层现今地应力优势方位、地应力垂向变化规律与机制开展综合研究，结果表明：（1）姬塬地区延长组长8储层水平最大主应力以近E-W方向为主，整体优势方向明显；（2）长8储层水平最大主应力、水平最小主应力分别介于49.17~65.68 MPa和41.87~56.31 MPa范围内，垂向主应力值最大，属正断型地应力机制，水平主应力差介于2.78~13.39 MPa，具备形成复杂压裂缝网的地应力条件；（3）岩性和岩石力学性质差异、埋深以及非连续结构面等因素是影响现今地应力垂向变化和地应力方向的主控因素；（4）垂向上压裂缝向上、向下均容易延伸，横向上压裂缝将优先沿水平最大主应力方向延伸扩展。研究成果有助于为研究区致密油的进一步勘探开发提供科学依据与地质参考。Abstract: The Yanchang Formation Chang 8 reservoir in the Jiyuan region of Ordos Basin is rich in tight oil resources. Quantitative characterization analysis of the present-day in-situ stress field is a key component to ensure profitable development. This study uses methods of imaging logging interpretation, in-situ stress experimental testing and conventional logging calculations to conduct a comprehensive study on the present-day dominant orientation, vertical variation patterns and mechanisms of in-situ stress in the Chang 8 reservoir. The results show that: (1) The horizontal maximum principal stress in the Yanchang Formation Chang 8 reservoir of Jiyuan region is mainly in the near E-W direction; (2) The horizontal maximum and minimum principal stress magnitude of the Chang 8 reservoir is in the range of 49.17~65.68 MPa and 41.87~56.31 MPa respectively. The vertical principal stress value is the largest, which belongs to the normal fault type in-situ stress mechanism. The horizontal principal stress difference is between 2.78~13.39 MPa, which inidcates the in-situ stress conditions to form a complex fracture network; (3) Factors such as differences in lithology and rock mechanical properties, burial depth, and discontinuous structural planes are the main controlling factors affecting the vertical changes and directions of present-day in-situ stresses; (4) Vertically, hydraulic fractures are easy to extend upward and downward, and they will preferentially extend along the direction of the horizontal maximum principal stress laterally. The research results will help provide scientific basis and geological reference for further exploration and development of tight oil in the study area.
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