塔里木盆地玉北1井背斜带变形特征与形成机制

Deformation characteristics and forming mechanism of the Well Yubei 1 anticline belt in the Tarim Basin

塔里木盆地玉北1井构造带形成过程与变形机制的解析,是揭示该带碳酸盐岩储层发育与展布规律的重要环节。断层及背斜轴面分析表明,该带发育两种类型构造。一种是贯穿南北的正花状构造;另一种上下构造层构造形态差异明显。上部为对称背斜,受高角度走滑断层控制;下部为不对称背斜,受沿寒武系膏盐层发育的逆冲断层控制。研究表明,玉北1井构造带定型期为中加里东期,此后至少叠加了晚加里东期与海西晚期两次区域变形。构造带沿走向主干断层倾向发生变化,自北向南由逆冲向走滑构造转变。在两条主干断层交汇部位背斜最发育,其核部有寒武系膏泥岩的汇聚,形成了剪切-挤压断层转折背斜。由此推断,构造带奥陶系碳酸盐岩层系不仅存在加里东期、晚海西期两期隆升剥蚀,而且在剪切-挤压背斜顶部、层间发育的高角度、低角度裂缝都为岩溶的形成提供了有利条件。

Interpretation of the development process and forming mechanism of Well Yubei 1 anticline belt in the Tarim Basin is an important part of study to map the carbonate reservoirs.Analysis of faults and axial planes of the anticlines reveals that two structural styles occur in the study area.One is positive flower structure which runs through the anticline belt in N-S direction.The other one shows significant difference in structural style between upper and lower structural layers.The upper layer is a symmetry anticline and is controlled by a high angle strike slip fault.The lower layer is a dissymmetry anticline and is controlled by a thrust fault developed along the Cambrian gypsiferous mudstone layer.Well Yubei 1 anticline belt was finalized in the mid-Caledonian period,and experienced at least two regional deformations in the late-Caledonian and late-Hercynian.However,the anticline belt changes along the inclination of the anticline,and is converted from a thrust structure to a strike-slip structure in N-S direction.The anticlines are most highly developed at the intersection of two main faults.The Cambrian gypsiferous mudstone was deposited at its core,resulting in a shear-compression anticline.On this basis,we believe that the Ordovician carbonate sequence not only experienced two stages of uplifting and erosion in the Caledonian and early Hercynian and the high angle and low angle fractures developed in the anticlines formed by shear-compression all which provided good conditions for the karstification.