同生逆断层对冲积扇沉积构型的控制作用机理

It has profound scholar meaning to study the effects of contemporaneous reverse faults on the formation and distribution pattern of alluvial fan sedimentary architecture in compressional basin margin. The investigation on coupling relationship between tectonics and sedimentation will deepen the sedimentology theory and the prospect results will have instructional guides on reservoir internal heterogeneity evaluation and oil exploration and development practices. The alluvial fan deposits of this study are located in Northwestern margin of the Junggar basin, and from the Triassic Karamay formation. The main research target is understanding the control mechanism of contemporaneous reverse faults on alluvial fan depositional architecture.The first step is building the formation structure model based on 3D seismic interpretation and dense well data to characterize the distribution characters of the contemporaneous reverse faults. Then, the balanced structual section analysis and the tectonic physical simulation experiments of the contemporaneous reverse faults will be used to study the formation and evolution of slope-break and normal traction in the fault formation process. The work in next step is building the alluvial fan architecture model based on the outcrop and dense well data and also the depositional architecture spatial differences are analyzed during the fine modeling building procedure. Finally,based on the previous study results ,the control mechanism of the slope-break and normal traction of contemporaneous reverse fault effects on alluvial fan architecture will be studied through comparision analysis and the flume experiment.

在挤压性盆地边缘，同生逆断层对冲积扇沉积构型形成与分布的控制作用机理研究对于深化沉积学理论、探讨构造与沉积的耦合关系、评价储层内部差异性并指导油气精细勘探和开发具有重要的理论和实际意义。本项目以准噶尔盆地西北缘克百地区三叠系克拉玛依组冲积扇为研究对象，以同生逆断层对冲积扇沉积构型的控制作用机理为研究目标，首先通过3D地震资料解释和密井网井资料分析建立精细的地层构造模型，表征同生逆断层的分布特征，并通过构造平衡剖面分析方法和构造物理模拟实验研究同生逆断层特别是断层坡折和正牵引构造的形成和演化过程；然后通过露头解剖和密井网井资料分析研究沉积构型的差异分布特征，建立精细的冲积扇沉积构型模型；最后，以前述构造演化与沉积构型研究为基础，通过比较分析和水槽模拟实验研究同生逆断层演化过程中断层坡折、正牵引构造等构造因素对冲积扇沉积构型形成与差异分布的控制作用机理及响应模式。

本项目通过露头测量、地下实例区钻测井及3D地震资料解释、构造物理模拟、水槽沉积模拟实验等方法，系统研究了同生逆断层对冲积扇沉积构型形成与分布的控制作用机理。结果表明：（1）同生逆断层上盘正牵引构造可分为背斜型和断鼻型两类，其中背斜型在平面上呈短椭圆状，凸起幅度较大，挤压变形较强烈，多伴生次级断层，而断鼻型在平面上呈半椭圆状，凸起幅度较低，挤压变形较弱；（2）干旱条件下的冲积扇由洪水期碎屑流和间洪期牵引流交替控制，洪水期是冲积扇主要生长期，在顺物源方向上依次发育槽流砾石体、片流砂砾体、洪水水道砂砾体及发散状径流水道砂体，而间洪期冲积扇上不定时发育小规模水道体系，并对洪水期槽流砾石体和片流砂砾体进行冲刷侵蚀并形成砂质充填的流沟体系，据此建立了干旱型冲积扇沉积构型模式；（3）同生逆断层正牵引构造对砂砾岩体分布特征和内部沉积构型具有强烈的控制作用，其中长轴方向垂直于古水流的正牵引构造在沉积过程中对泥石流形成阻挡，造成一部分较粗粒沉积物优先卸载在正牵引构造迎水面附近，形成向源逆向增生的砂砾坝，并导致水流方向发生偏转，从正牵引构造长轴两端进入盆地边界断层下盘发生沉积，而长轴方向平行于古水流方向的正牵引构造往往将逆断层上盘隔为多个相对独立的区域，并限制了砂砾质沉积物的侧向搬运，导致各区域内物源供给、砂砾岩体厚度与叠置样式存在较大差异；此外，不同幅度的正牵引构造对于古水流的控制作用强度不同，进而形成不同的沉积构型样式；（4）断裂坡折带对冲积扇沉积过程和内部构型具有显著的控制作用，在其坡度较大、坡长较小时，冲积扇多沉积于坡前，形成多期侧向叠置的超厚层冲积扇，随着坡度减小、坡长增加，冲积扇逐步倾向于沉积在坡上，侧向上迁移频次逐步增加，冲积扇厚度减薄、面积增大。