辽河东部凸起太原组页岩孔隙分形特征

Pore Fractal Characteristics of Taiyuan Formation Shale in Eastern Uplift of Liaohe Depression

页岩孔隙结构具有良好的分形特征,孔隙结构的分形维数能定量描述孔隙结构的复杂程度。以辽河东部凸起为例,应用高压压汞方法研究了页岩孔隙结构及其不规则性,计算了页岩孔隙分形维数。研究结果表明,辽河东部凸起太原组页岩孔隙分形无标度区为0.09～60μm,孔隙分维数为2.378～3.007,随着分形维数的增大,页岩的非均质性增强,压汞实验得出的页岩孔径分布特征也证明了页岩的孔隙分形维数可以用来定量描述页岩储层岩石孔隙结构的微观非均质性;数学拟合表明分形维数与有机质含量相关性差,反映页岩中无机孔隙为主体孔隙类型;分形维数与石英含量呈较弱的正相关而与黏土矿物含量呈较强的负相关性,表明黏土矿物含量对页岩孔隙结构影响明显。分形维数与页岩的渗透率和孔隙度均具有很好的负相关性,分形维数越大,岩心的渗透率和孔隙度越小,表明分形维数越大,孔隙结构越趋于复杂,不利于气体的渗流和产出。

Pore structure in shale is well featured by fractal property and the fractal dimension can be used to quantify the complexity of the pore structure.High pressure mercury intrusion was used to analyze the pore structure and the pore fractal dimension was also calculated.The study demonstrates that the pore fractal scale-free range of Taiyuan shale（C3t）in eastern uplift of Liaohe Depression is 0.09-60μm and pore fractal dimension 2.378-3.007.The shale with larger pore fractal dimension also shows stronger pore heterogeneity.Pore diameter distribution tested by high pressure mercury intrusion also indicates that pore fractal dimension is practicable to describe quantitatively the heterogeneity of pore structure in shale.Poor correlation between pore fractal dimension and organic content indicates that the pore system in transitional shale is mainly composed of inorganic pores.Weak positive correlation in quartz content with strong negative correlation in clay content indicates that the influence from clay content is much more significant for shale pore structure.Negative correlation existing between pore fractal dimension and permeability and porosity of shale indicates that the more complex the pore structure is,the more difficult it is for the shale gas to flow and produce.