渤海湾盆地渤南洼陷古近系沙河街组三段沉积相的GIS辨析

Analysis based on GIS of sedimentary facies of the Member 3 of Paleogene Shahejie Formation in Bonan Sag,Bohai Bay Basin

渤海湾盆地济阳坳陷渤南洼陷的主要含油层系为古近系沙河街组三段,目前关于该段沉积相类型的认识分歧很大。应用地理信息系统ArcViewGIS3·2a的空间分析功能,求取了沙三段各砂层组的沉积表面坡度。9砂层组沉积时的坡度多为1·5°～3·5°,紧邻孤岛凸起处坡度可达3·5°～5°;而5砂层组沉积时的坡度则几乎全部小于1·8°。综合考虑5砂层组、9砂层组的代表性和盆地沉积构造背景、储集层砂体外围泥岩的沉积特征、纵向上的沉积组合关系、储集层砂体平面展布形态及其自身的沉积学特征,认为渤南洼陷沙三段主要的储集层砂体应为辫状河三角洲沉积,仅最下部9砂层组的储集层砂体为深水湖泊重力流沉积。

The Member 3 of Paleogene Shahejie Formation is the main petroliferous interval in the Bonan Sag of Jiyang Depression in Bohai Bay Basin. Currently the viewpoints about the sedimentary facies types are quite different. The sedimentary gradients of each sandy interval of the Member 3 of Shahejie Formation were calculated by applying the spatial analysis module of geographic information system Arc- View GIS 3.2 a. The sedimentary gradient of the 9th sandy interval is mainly between 1.5^o - 3.5^o and the gradient where it is adjacent to the Gudao Uplift can reach 3.5^o-5^o, while the sedimentary gradient of the 5th sandy interval is generally less than 1.8^o. According to the representative features of these two sandy intervals, the depositional and tectonic setting of the basin, the sedimentary characteristics of the mudstones surrounding the reservoir sandbodies, the vertical sedimentary assemblages, the planar distilbution of the reservoir sandbodies and their own sedimentary characteristics, it is concluded that the main reservoir sandbodies of the Member 3 of Shahejie Formation in the Bonan Sag is dominated by braided flu- vial deltaic deposits and only the 9th sandy interval at the basal part of the Member 3 is of deep-water turbidite origin.