鄂北杭锦旗地区下石盒子组沉积相演化及控制因素

Sedimentary Facies Evolution and Controlling Factors of Lower Shihezi Formation in Hangjinqi Area,North Ordos Basin

通过对鄂尔多斯盆地杭锦旗地区钻井岩芯的岩石类型、沉积特征、剖面结构等特征的综合认识,结合测井资料的详细研究,对杭锦旗地区二叠系下石盒子组进行了沉积环境分析。结果表明:杭锦旗地区下石盒子组主要发育河流相和三角洲相,东部发育冲积扇;在山西组沉积基础上,受自身沉积特征控制,伴随古地貌继承性发育、构造运动变化、物源供给减少及古气候变化等原因,盒1-盒3沉积时期辫状河水道的规模不断减小,下石盒子组晚期,逐渐向曲流河过渡,主要发育河道和三角洲平原亚相;受近物源影响,砂体呈南北向展布,侧向上不连续。

By comprehensive understanding of the rock type, sedimentary characteristics, profile structure and other features of the drilling cores in Ordos Basin Hangjinqi areas,and combining with a detailed study of the logging data, the authors analyzed the sedimentary environment of permian Lower Shihezi Formation in the Hangjinqi area. All the results suggest that Lower Shihezi Formation in the Hangjinqi area mainly developed into fluvial and delta facies, and the eastern from alluvial fan. On the basis of the Shanxi Formation deposition,and because of being controlled by its own sedimentary features, as well as the inherited development of palaeogeomorphology, changes in the tectonic movement,reduction in source supply and ancient climate change etc., the braided river course decreased from Pl x^3 to P1 x^3 in size, and gradually converted to the meandering river in the late Lower Shihezi Formation,and the region during this period mainly developed into the river course and delta plain subfacies. Affected by the source of near objects, sand bodies spread from north to south and were laterally discontinuous.