焉耆盆地宝北构造三工河组裂缝形成机制及控制因素

Analysis of Fracture Generation Mechanism and Controlling Factor:An Example from Sangonghe Formation of Baobei Structure in Yanqi Basin

根据焉耆盆地宝北构造三工河组岩心裂缝的实际观测及宝北区块的局部构造特征,从背斜和断层两方面对局部应力场和裂缝发育特征进行解析,认为宝北构造的裂缝组合模式为:顺层滑脱裂缝+纵张裂缝+高角度共轭剪切裂缝+中、低角度共轭剪切裂缝+左阶张裂缝。前两者与背斜的形成和发展密切相关,后三者受控于断层的诱导作用。选取裂缝线密度和不同的参数进行拟合计算,认为控制顺层滑脱裂缝的因素为煤层总厚度及与背斜轴线的距离;断层诱导裂缝的控制因素为与大断裂的距离。依据在控制因素调解下的内插和外推,对宝北构造的综合裂缝密度进行了预测。

On the basis of the core fracture observation of Sangonghe Formation and the analysis of partial structural features of Baobei structure in Yanqi Basin, investigates the partial stress field and the fracture growing feature from the aspects of anticline and fault. The combinational fracture model is shown as follows: bedding detaching fractures, longitudinal tensile fractures, high angle conjugate shear fractures, middle/low angle conjugate shear fractures and left-lateral tensile fractures. The two former types are related to the formation and development of the anticlines, the three latter types are controlled by the fault induction. Through the fitting calculation based on choosing the fracture line density and different parameters, it is hold that the thickness of coal bed and the distance from anticlines axis dominate the developing degree of bedding detaching fractures and the fault inducting fractures arc controlled by the distance from great faults. According to the interpolation and extrapolation under the conciliation of controlling factor, the synthetical fracture density of Baobei structure is predicted.