元坝中部断褶带须家河组裂缝分形特征

针对四川盆地元坝中部断褶带须家河组岩体在构造应力场作用下的破裂具有良好的自相似性和分形特征，开展了须家河组断裂发育的分形特征和取芯段裂缝的分形特征研究，研究中采用箱形覆盖法来求取断裂和裂缝分维值，利用数学公式将各子区域的断裂容量维与岩芯裂缝容量维通过岩芯裂缝密度进行拟合，建立二者的定量关系，获得了四川盆地元坝中部断褶带须家河组有利的裂缝发育带。结果表明，须家河组裂缝分维值大于1.45的区域为裂缝发育区，油气富集程度高；裂缝分维值大于0.95且小于1.45的区域为裂缝较发育区；裂缝分维值小于0.95的区域为裂缝欠发育区。

Fractal Characteristics of Fracture of Xujiahe Formation in Fault-fold Belt of Central Yuanba Area

Fractures in the rock masses of the Xujiahe Formation in the fault-fold belt of the central Yuanba area of the Sichuan Basin are characterized by good self-similarity and fractal characteristics that are attributed to the tectonic stress field. Thus, this research is conducted with respect to the fractal characteristics of fault developments in the Xujiahe Formation, as well as factures in the rock core. The box-covering method was employed in this study to derive the fractal dimension values of faults and fractures. Further, using the fracture density in the core, mathematical formulae were adopted to fit the capacity dimensions of faults in each sub-area, as well as factures in the rock core, where the quantitative relation thereof was established. In this manner, the favorable fracture development zone of the Xujiahe Formation in the fault-fold belt of the central Yuanba area of the Sichuan Basin is obtained. The results show that the areas where the fractal dimension value of fractures in the Xujiahe Formation exceeds 1.45 belong to the fracture development zones, which are characterized by a high level of oil and gas enrichment and accumulation. The areas with fractal dimension values ranging from 0.95 to 1.45 are the relatively developed fracture zones, while areas with less than 0.95 are underdeveloped fracture zones.