关键词: 水泥环, 纤维水泥, 阻裂作用, 镜像分析, 微裂纹, 力学模型, 实验研究

Abstract: The surface of cement sheath in well bore is easy to be fractured. The fiber was used to improve the toughness of cement. When suffered from stretching, compression and perforation, the cement surface produced some cracks. Based on scanning electronic microscope, the analysis on fractured surface of fiber cement indicates that the intension of micro crack in cement can partly be increased because the existence of fiber leads to the enhancement of compressive strength of cement. The stress intensity factor of cement can also be reduced because the existence of fiber can improve the ability of resistance to rupture of cement and make the toughness of cement strengthen. The fiber-matrix interface can prevent the crack from propagating in cement whether the propagation trend of crack is vertical or congruent to the stretch direction of fiber. Fiber can prevent the fracture from seriously extending during the fiber cement being exerted compression, stretching and perforation. Thus the toughness of cement can be strengthened, which is helpful to ensure the success of perforating completion operations. Based on the analysis of experiments phenomena, the crack resistance mechanism of fiber cement was analyzed and its mechanical model was built up.

Key words: cement sheath, fiber cement, fracture-resisting ability, SEM analysis, micro crack, mechanical model, experimental study