多孔介质微观孔隙结构分形特征及分形系数的意义

依据孔隙结构的球体模型和毛管束模型 ,推导出两种模型的孔隙体积表达式和两种模型分形维数间的关系式。计算结果表明 ,基于毛管束模型的分形维数总比基于球体模型计算的分形维数小 1,分形系数的物理意义在于它反映了孔隙的发育程度。基于毛管束模型 ,利用压汞数据计算了西峰油田长 8储层多孔介质微观孔隙的分形维数 ,同时给出了分形维数与孔隙度、渗透率等地层参数的关系曲线。分析结果表明 ,该区孔隙结构具有分形特征 ,分形维数为 1～ 2。分形维数越大 ,多孔介质微观孔隙分布的非均质性越强 ;分形系数越大 ,孔隙越发育 ,储层物性越好。

Fractal characteristics of micropore structure of porous media and the meaning of fractal coefficient

On the basis of the ball model and capillary model for pore structures, the pore volume expressions and the relational expressions of fractals for the two models were developed. The results show that the fractal dimension value based on capillary model is one less than the fractal dimension based on ball model. The fractal coefficient means the development degree of pores. The fractals of micropore structure of porous media in Chang 8 Formation of Xifeng Oilfield were calculated on the basis of the capillary model, and the correlation curves of fractals with porosities and permeability were given. The analysis results indicate that the micropore structure of Chang 8 Formation possesses fractal characteristics, and the fractal dimension is from one to two. The higher the fractal dimension is, the more serious the heterogeneity of micropore distribution will be. The development of pores and the physical properties of reservoir get better with the increment of the fractal coefficient.