二连盆地善南洼槽阿三、阿四段层序地层特征与沉积演化

Sequence Stratigraphic Characters and Sedimentary Evolution in 3rd and 4th Members of Aershan Formation in Shannan Sag of Erlian Basin

基于层序地层学原理和研究方法,综合利用岩心、钻井、测井以及地震反射等标志,将善南洼槽阿尔善组阿三、阿四段划分为一个三级层序,并细分为低位、湖侵和高位体系域,建立以体系域为单元的等时地层格架;在此基础上,分析了沉积相的构成、分布和演化规律,认为该区主要发育近岸水下扇、扇三角洲、湖泊和浊积扇4大沉积体系,南北两侧陡坡带主要发育近岸水下扇沉积体系,东西两侧缓坡带主要发育扇三角洲沉积体系,湖泊相发育在洼槽中央。综合分析各层序沉积特征及演化规律,指出了善南洼槽有利的勘探区域。

Based on the principle of sequence stratigraphy and research methods,the 3rd and 4th members of Aershan Formation in Shannan Sag were divided into 1 third-order sequence and subdivided into low stand,lake transgression and high stand system tracts according to core,drilling,logging data and seismic reflective marker,the isochronal stratigraphic framework was established with one system tract as a unit.On the basis of the study,the architecture,the rules of distribution and evolution of sedimentary facies were analyzed.It is considered that there developed 4 sedimentary systems including near-shore underwater fans,fan delta,lacustrine and turbidite fans.Near-shore underwater fans are developed in steep slope on the north and south side of the sag,fan delta is developed in gentle slope on the west and east side of the sag,and lacustrine is developed in the center of the sag.By a comprehensive analysis of sedimentary characteristics and evolution law,the favourable exploration areas in Shannan Sag are pointed out.