镇北地区长7段辫状河三角洲沉积相研究

Sequence stratigraphic and sedimentary modes of lacustrine braid-deltas in Chang 7 Member of Zhenbei area, Ordos Basin

结合区域构造-沉积背景,分析研究区岩心、测井、地震资料得出,鄂尔多斯盆地镇北地区上三叠统延长组长7段发育典型坡陡型辫状河三角洲-浊积沉积。以层段内稳定发育的细粒段为对比标志层,将其划分为1个长期旋回,细分为5个中级旋回,建立了具有时间意义的层序地层格架。平面上明确了各旋回依次发育辫状河三角洲、浊积体及湖泊沉积,垂向上明确了各期辫状河三角洲整体进退幅度较小,仅辫状河三角洲前缘与前三角洲部分叠置;得出了储层成因类型以水下分流河道和浊积水道为主,并指出斜坡古地形作为主控因素,控制了湖平面变化及沉积体系的展布。该研究不仅为辫状河三角洲沉积层序地层划分和对比提供了思路与方法,同时也为油田的下一步滚动勘探开发提供依据。

Based on the regional tectonic sedimentary background and analysis of the core,logging and seismic data,it is concluded that a typical slope braid-delta,turbidite deposit,is developed in the Chang 7 Member of Upper Triassic Yanchang Formation of Zhenbei area,Ordos Basin.Taking the fine-grained segment of stable development in the layer as the m arker horizon,it is divided into one long-term cycle and subdivided into five intermediate cycles,and a sequence stratigraphic framework with time significance is established.It is clear that braid-delta,turbidite and lacustrine deposits are developed in each cycle,and the braid-delta has a smaller overall advance in the vertical,only the braid-delta front and the front delta are overlapped.The formation of the reservoir is mainly based on the underwater distributary channel and turbidite channel,and it is pointed out that the slope paleotopography is the main controlling factor,which controlled the change of the lake level and the distribution of the depositional system.The study not only provides ideas and methods for the stratigraphic division and comparison of the stratigraphic stratigraphy of the braid-delta,but also provides a basis for the next rolling exploration and development of the oil field.