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基于低温氮吸附试验的页岩孔隙分形特征研究

Study on fractal features of shale pore based on low temperature nitrogen absorption experiment

  • 摘要: 为了对页岩孔隙结构特征进行更加精细地评价,需要对页岩孔的低温氮吸附试验数据进行综合分析。运用分形理论,分析了不同孔类型表面积分形维数D_b和体积分形维数D_t特征,对比了分形维数与孔隙结构特征参数之间的相关关系。结果表明:半封闭型墨水瓶状孔(具有Ⅰ类吸附回线)的D_t大于2.8,四周开口型平行板状孔(Ⅲ类)D_t为2.6~2.8,四周开口型尖劈状孔(Ⅱ类)D_t为2.2~2.6;D_b和D_t分别与平均孔径、BET比表面积、BJH总孔体积、有机碳含量TOC和类镜质组反射率Ro具有明显相关性。页岩孔隙分形特征显示,D_b和D_t分别指示了孔隙内表面和空间形态的复杂程度,可用来定量表征页岩储层微孔结构及地球化学特征。

     

    Abstract: In order to more finely evaluate the porous structure features of the shale,a comprehensive analysis should be conducted on the data of the low temperature nitrogen absorption experiment A fractal theory was applied to analyze the features of the different pore type surace fractal dinension D, and the volunme fractal dmension D, and to compare the corelation relatonship between the fractal dimension and theporous structure featre parameters: The results showed that the D, valueof an ink-botle type alf losed pore( with Type l adsorption loop) was over 2.8,the D,value of a periphery open pore type parlleu plate pore(TypeⅢ) was ranging fromn2.6 ~ 2.8 and D, value of a periphery op.en type spire pore(Type Ⅱl)was 2.2~2.6.The D, and D,indridually had obicus core ato reationship withthe average pore size,ET specfic surtace BJH total pore volume.organic carbon contentToc and virnite refectance Ro.The porous fractal features of the shale shovwed that the D,and D individull could indicate the complexity of the pore inemnal surace and space fom could be applied to quanitaivel express he micopore stoucture and the geochemical features of the shale reservoirs.

     

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