石油与天然气地质 ›› 2019, Vol. 40 ›› Issue (3): 653-660.doi: 10.11743/ogg20190320

• 开发工程 • 上一篇    下一篇

页岩结构面特征及其对水力压裂的控制作用

李晓1,2,3, 赫建明1,2,3, 尹超1,2,3, 黄北秀1,2,3, 李关访1,2,3, 张召彬1,2,3, 李丽慧1,2,3   

  1. 1. 中国科学院 地质与地球物理研究所页岩气与地质工程重点实验室, 北京 100029;
    2. 中国科学院 地球科学研究院, 北京 100029;
    3. 中国科学院大学 地球与行星科学学院, 北京 100049
  • 收稿日期:2019-03-01 修回日期:2019-03-20 出版日期:2019-06-28 发布日期:2019-04-26
  • 第一作者简介:李晓(1961-),男,博士、教授,博士生导师,工程地质力学。E-mail:lixiao@mail.iggcas.ac.cn。
  • 基金项目:
    国家自然科学基金项目（51579137）。

Characteristics of the shale bedding planes and their control on hydraulic fracturing

Li Xiao1,2,3, He Jianming1,2,3, Yin Chao1,2,3, Huang Beixiu1,2,3, Li Guanfang1,2,3, Zhang Zhaobin1,2,3, Li Lihui1,2,3   

  1. 1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
    2. Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China;
    3. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2019-03-01 Revised:2019-03-20 Online:2019-06-28 Published:2019-04-26

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摘要： 页岩是沉积岩中的一种，具有十分明显的层理构造。探究页岩层理结构面对其水力压裂行为的影响，对页岩气的开采具有重要意义。通过对鄂尔多斯盆地南部延长组页岩不同尺度下（米级到十微米级）沉积结构特点的分析，结合不同层理倾角条件下的大尺寸页岩试样水力压裂试验，研究了页岩结构面（层理面）的特征及其对水力压裂过程和结果的控制作用。结果表明，米级、分米级、厘米级、毫米级和10微米级等不同研究尺度下的纹层平均厚度分别为2.26 m，2.09 dm，1.70 cm，1.48 mm和11.7μm，呈现出分形特征，且分形维数为1.06。页岩水力压裂行为受层理结构面影响显著，主要体现在压裂前后裂缝形态对比与破裂压力两个方面。层理倾角小于30°时，页岩试样压裂前后裂缝形态对比明显，新生裂缝较多，破裂压力较大，且随着层理倾角的增大急剧减小；大于45°时，压裂前后试样的裂缝形态几乎没有改变，破裂压力较小，且随着层理倾角的增大呈现小幅度的波动；整体上不同层理面角度下页岩的破裂压力呈斜“S”型变化。试验中的裂缝扩展，水压曲线以及破裂压力随层理倾角的不同均发生变化。

关键词: 破裂压力, 裂缝, 结构面, 纹层, 页岩, 水力压裂, 延长组, 鄂尔多斯盆地

Abstract: Shale,a kind of sedimentary rocks,is characterized by significant bedding.The investigation of the impact of bedding planes of shale on hydraulic fracturing is of great significance for the exploitation of shale gas.The characteristics of sedimentary structures at various scales (ranging from meter to ten micron scales) of shale in the Yanchang Formation in southern Ordos Basin were analyzed,and the hydraulic fracturing tests for multi-sized shale specimens under different dip angles of bedding plane were carried out,both of which function to explain the characteristics of the bedding planes of shale and their controlling effects on hydraulic fracturing process and outcome.The results show that the average thickness of laminae is of fractal features with a fractal dimension of 1.06,and is 2.26 m,2.09 dm,1.70 cm,1.48 mm and 11.7 μm,corresponding to meter,decimeter,centimeter,millimeter and 10-micron scales respectively.The behaviors of hydraulic fracturing are significantly influenced by the bedding planes of shale,clearly shown by the contrast of fracture geometry before and after fracturing and the fracturing pressure.When the dip angles of the bedding planes are less than 30°,the fractured shale specimen is remarkably different from its original one in fracture geometry,featuring much more artificial fractures,and higher fracturing pressure,which tends to slump as the dip angle of bedding plane increases; while when the dip angles of the shale specimens are above 45°,the fracture geometry of the shale specimens after fracturing is almost the same with that of the original specimens,featuring lower fracturing pressure which tends to fluctuate a little with the increase of the dip angle of the bedding planes.Generally,the fracturing pressures of shale under different dip angles of bedding plane fluctuates in the shape of oblique "S".Besides,the controlling effects of structural dip angles of the bedding planes on the fracture propagation,hydraulic pressure curve and fracturing pressure are also reflected in the tests.

Key words: fracturing pressure, fracture, bedding plane, lamina, shale, hydraulic fracturing, Yanchang Formation, Ordos Basin

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