【摘要】 以南华北盆地户部寨第三系沙河阶组粉砂岩低渗透储层为例,总结了其中发育的5种类型构造裂缝组合,即:①南北向雁形张节理组成的共轭剪节理带;②东西向雁形张节理组成的共轭剪节理带;③缠结状多组剪切构造裂缝;④组合状交切的多组剪切构造裂缝及张裂缝;⑤散状无序排列的构造裂缝。在此基础上,建立光弹性试验构造物理模型,沿现应力场96°方向,均匀地对该模型逐步增加外载力。结果表明,沿各组合裂缝尖端分别形成对称于裂缝走向、且主轴垂直于裂缝的Ⅰ型等色线条纹;对称于裂缝走向、且主轴平行于裂缝走向的Ⅱ型条纹和斜交于裂缝走向的复合型(Ⅲ型)条纹。第①类组合裂缝尖端以Ⅰ型等色线条纹的拉张应力和张剪应力为主;第②类组合裂缝尖端以复合型(Ⅲ型)等色线条纹的挤压应力为主;第③、④和⑤类组合裂缝尖端的应力分布较为复杂。当模型外载荷接近1000kg时,裂缝尖端起裂,并开始发育显微裂缝,而当外载荷达1100-1200 kg时,沿裂缝尖端部位形成宏观裂缝,并开始扩展。5种类型的裂缝组合扩展发育程度由强至弱依次为:①,③,⑤,②,④。其中第①类共轭裂缝组合起裂最早,扩展最快,裂缝间的连通趋势最好,说明规则分布的构造裂缝组合,在垂直于外施加载衙时更易达到连通的目的。更多还原

【Abstract】 Five types of fracture assemblage were summarized from the siltstone of the Tertiary Shahejie Formation in the southern North China basin, i. e. , (1) conjugated shear fracture belts arranged in en echelon N-S-striking tension fracture; (2) conjugated shear fracture belts arranged in en echelon E-W-striking tension fracture; (3) tangly shear fractures with variable striking; (4) shear and tension fractures cutting each other; and (5) sporatic fractures. Furthermore, a photoelastic physical model for experiment was established with well-proportioned and gradually increased loading along the direction of 96°(ESE-WNW). The results suggest that 3 types of isochrome map, which marks the local stress along the fractures, could be identified: type Ⅰ has a symmetrical shape in respect to the fracture with the main axis perpenticular to the fracture, and type Ⅱ has a symmetrical shape in respect to the fracture with the main axis parallel to the fracture, whereas the compound type (type Ⅲ) has an asymmetrical shape in respect to the fracture with the oblique main axis. Fracture assemblage of type (1) has type I isochrome map with tensional or tensional-shear stress, and fracture assemblage of type (2) has compound type (type Ⅲ) isochrome map with compressional stress, and fracture assemblage of type (3), (4) and (5) have very complicated stresses. Micro-fracture starts to form when loading is increased to 1000 kg, and macro-fracture starts to extend when loading is increased to 1100-1200 kg. The order of the extending of broken fracture from strong to weak is (1), (3), (5), (2) and (4). The fracture assemblage of type (1) is the earliest one to start tension with the greatest tensional velocity; Therefore, the fact that the best tendency to connect the fractures occurs to type (1) suggests that a perpendicular loading to the en echelon fracture could easily result in the occurrence of connectedness.更多还原