Abstract:

Based on the field observation and description, the factors relevant to the mechanism of fault deformation and the process of fault zone structure evolution in carbonate rock are systematically discussed, and the relationship between fault zone structure and fluid flow in the carbonate formation is analyzed. The research shows that the relevant factors to the mechanism of fault deformation in carbonate rock include lithology, porosity, deformation depth, temperature, cementation, pre-existing fractures and so on, and the factors controlling the formation of fault zone structure include sliding displacement and fracture mode. Low-porosity carbonate rock is characterized by fracture, while for high-porosity carbonate rock, deformation zone developed in the early time of deformation, fractures gradually connected and developed into fault zone. With burial depth increasing the structure of fracture zone is changing: when the burial depth is less than 3 km, the core of fault mainly develop into fault breccias and fault gouge without cohesion; when the burial depth is more than 3 km, the core of fault mainly develop into fault breccias and cataclasite with cohesion and fractures of various causes developed in the fracture zone. With the depth increasing, fracture mode changes from early fracturing into late cataclasis, eventually cataclastic flow. Fracture zone evolution is a four-dimensional process, the development of fault core and fracture zone, directly affects faults on hydrocarbon migration and seal. The research on the mechanism of fault deformation, the internal structure of fault zones and the fluid migration, can provide important theoretical basis for seal.

Key words: carbonates, fault zone structure, physical characteristics, control fluid accumulation