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利用Barre花岗岩在不同封闭压力(0.5～5kbar)下所做的四种形变实验得到的裂缝组进行了裂缝空间分布长度的康托尔粉尘型分形分析。用偏光显微镜方法画出的裂缝按成因分成以下几种:剪切裂缝、张性裂缝、松弛裂缝或减压裂缝。我们发现,对所有裂缝组来说,其裂缝的分布都类似于对数正态频数分布。在给定的实验中,不同方位的裂缝,其平均长度间的差别随着压力增加而减小,即所有方位(应力源)的裂缝长度总是随着封闭压力的增加而变得更加一致。线性康托尔粉尘分析方法也适用于裂缝组。这些分析表明:在样品中,所有裂缝的分形维数随着封闭压力的增加而微弱增加,而样品中(剪切缝、张性缝、减压缝)各个裂缝组间的分形维数的差别往往随封闭压力的增加而减小。在最小封闭压力实验中,我们发现:对不同成因的裂缝,在裂缝长度和分形维数上都存在着最大的差异。这一分析表明:我们能用分形维数和长度来描述裂缝油田内裂缝类型的差异。而且这种分析方法也适用于从各向异性应力场到由于封闭压力增加变得更均匀的应力场的各种应力场。因而我们能从脆性裂缝到塑性形变中测量裂缝类型的变化。
The Cantor dust fractal analysis of the spatial distribution of fractures was carried out by using the fractures obtained from Barre granite under four different deformation pressures (0.5 ~ 5kbar) under different confining pressures (0.5 ~ 5kbar). Fractures drawn by polarization microscopy are classified into the following categories by causes: shear, tension, relaxation, or pressure relief. We find that for all fracture groups, the distribution of fractures is similar to that of log normal frequency distribution. In a given experiment, the difference in average length between fractures of different orientations decreases with increasing pressure, ie the fracture length of all azimuths (stressors) always becomes more consistent with the increase of blocking pressure. Linear Cantor dust analysis method also applies to the fracture group. These analyzes show that the fractal dimension of all fractures increases slightly with the increase of the confining pressure in the sample, and the difference of the fractal dimension among the various fracture groups in the sample (shear, tension and decompression) Often with the increase of closure pressure decreases. In the experiment of minimum confining pressure, we find that there is the biggest difference in crack length and fractal dimension for different causes of fractures. This analysis shows that we can use fractal dimensions and lengths to describe the differences in fracture types within fractured oil fields. Moreover, this method of analysis also applies to various stress fields ranging from anisotropic stress fields to more uniform stress fields due to the increase of confinement pressure. Thus we can measure changes in the type of fracture from brittle fracture to plastic deformation.