高邮凹陷古近系戴南组扇三角洲沉积体系及其沉积相模式

扇三角洲是苏北盆地高邮凹陷戴南组较为发育的一种沉积类型,集中分布在凹陷南部陡坡带一侧,是该区一个重要的勘探领域。根据岩芯、测井、地震、粒度等资料,对高邮凹陷古近系戴南组扇三角洲的沉积特征进行了研究,建立了高邮凹陷戴南组的沉积相模式。根据单井沉积相、连井沉积相分析以及地震剖面反射特征和砂地比图综合分析,确定了戴南组各亚段沉积相的平面展布,编制了戴南组各亚段沉积相分布图。结果表明:高邮凹陷南部陡坡带地形陡,存在扇三角洲发育的条件,也存在反映浅水环境的岩性特点,成分成熟度和结构成熟度低反映了近物源的条件,还发现反映牵引流和重力流共存的沉积构造特点;从地震反射特征上看,反射结构不稳定,并发现向盆地边缘加厚的楔形地震相。在此基础上,重点对戴南组扇三角洲相各微相进行了分析,共划分出扇三角洲平原、扇三角洲前缘和前扇三角洲亚相,并进一步划分出水上分流河道、漫滩沼泽、水下分流河道、分流河道间和席状砂等微相,最后详细阐述了各微相的沉积特征。

Fan delta sedimentary system and facies models of Dainan Formation of Paleogene in Gaoyou Sag

Fan delta,which is developed on the steep slope belt on the south side of the sag,is an important sedimentary facies of Dainan Formation in Gaoyou Sag of Subei Basin.It is a very important oil exploration area in Gaoyou Sag.According to the data of core,well-log,seismic,granularity analysis and other information,a comprehensive study on fan delta sedimentary characteristics of Dainan Formation of Paleogene in Gaoyou Sag were conducted,and the sedimentary facies models of Dainan Formation were established.According to single well and cross well sedimentary facies analysis,seismic profile reflection and sand ratio contour map analysis,planar distributions of sedimentary facies in different submembers of Dainan Formation were confirmed,and the distribution maps of sedimentary facies in different submembers were drawn.The results showed that the steep slope paleogeography in the southern part of Gaoyou Sag was a suitable condition for the development of fan delta,and the lithologic characters reflecting shallow water environment were discovered,and the low component and textural maturities reflected the conditions of near provenance of sediments,and sedimentary structures reflecting traction flow and gravity flow were found;based on the seismic reflection profile,the reflection configuration was unstable,wedge shaped seismic facies toward the edge of the basin was developed.Finally,fan delta was divided into three parfacies including fan delta plain,fan delta front and fore fan delta,and further divided into some microfacies including distributary channel on water,back marsh,underwater distributary channel,inter distributary channel,sheet sand and so on;the sedimentary characteristics of the microfacies were detailedly explained.