黄骅坳陷沙一段物源分析及地质意义

Analysis of sediment provenance and its geological significance in the first member of Shahejie Formation,Huanghua Depression

黄骅坳陷不同区块的勘探程度相差较大,从整体出发分析物源对确定湖盆内沉积体系的展布显得十分重要。应用数理统计的方法,结合重矿物组分、碎屑组分、石英含量、砂岩厚度及含量和地震反射结构等资料对黄骅坳陷沙一段的物源方向进行了综合分析,并据此预测了沉积体系的类型和展布特征。结果表明,黄骅坳陷沙一段存在北部、东部、西北部、西部和东南部5个物源区,其中北部和西部为主要物源区,北部物源对南部地区的影响较大。根据物源及多种资料综合分析,沙一段存在7类沉积体系,多期多物源继承性发育的砂体广泛分布,以近岸水下扇、辫状河三角洲、三角洲、重力流、滑塌浊积扇和滨浅湖滩坝砂体为主要储集体类型。离物源区最远的三角洲水下分流河道和河口坝砂岩储集物性最好,其次为辫状河三角洲水下分流河道和河口坝砂体,重力流及近岸水下扇离物源区最近,储集物性最差。

Exploration degree in the different blocks of Huanghua Depression has large difference so that systematic analysis of the sediment provenance is very important for the definition of the distribution of sedimentary facies in a lacustrine basin. Comprehensive research on provenance has been made with the application of mathematical statistics methods,combined with analysis of heavy mineral component,detrituscomponent,quartz content,thickness and content of sandstones,and seismic reflection structure of the first member of Shahejie Formation( Es1 ) in Huanghua Depression. Distribution features of sedimentary system were forecasted based on the provenance. There are five provenance areas in Es1 formation,namely north area,east area,northwest area,west area and southeast area ,of which the north area and west areaare the dominant ones. The south sedimentary area is influenced partly by the north provenance area. According to the comprehensive interpretation from provenance analysis and other analysis of sedimentary facies,seven depositional systems were defined in Es1 formation,inwhich multi-period,multi-provenance and successive sand bodies developed widely and deposited primarily in nearshore subaqueous fans,braided deltas,deltas,gravity flow,slump turbidite fans and beach-bar in shore-shallow lake. The physical property of the sandstones of underwater distributary channel and mouth bar of delta far from the provenance is the most favorable,and that of the sandstones of underwaterdistributary channel and mouth bar of braided deltas is suboptimal. The sandstones of gravity flow and offshore subsea apron nearest from theprovenance have the lowest value of physical property.