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。
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 6chelon N-S-striking tension fracture; ② conjugated shear fracture belts arranged in en échelon 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 ） 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 Ⅱ ） 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 6chelon fracture could easily result in the occurrence of connectedness.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2005年第5期602-607,共6页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号40472106
40434011
40172070)中原油田勘探开发研究院资助的成果。
