【摘要】 综合地震、测井及岩心等资料表明,辽西凹陷北洼古近系沙河街组存在完整的地层序列,其可划分为5个三级层序.沙一段和沙二段之间不存在不整合层序界面;SQs3-1(沙三上段)在相对隆起区遭受剥蚀,但在坳陷带内发育完整.沙河街组发育的主要沉积体系包括扇三角洲、辫状河三角洲、近岸水下扇、滨浅湖滩坝等,其分布受到了同沉积断裂、次级古隆起、古坳陷分布的制约.研究区内有利的储集体包括分布于古隆起边缘低位体系域的砂体、洼陷中部的深水重力流砂体、古隆起高部位的碳酸盐岩等.它们与下部沙三段发育的大套暗色泥岩及上覆的沙一段泥质层可形成良好的生储盖组合,并在古隆起边缘、次级洼陷带、断裂坡折带及缓坡边缘形成岩性地层圈闭.更多还原

【Abstract】 The existence of a complete stratigraphic sequence in Paleogene Shahejie Formation in northern Liaoxi depression is confirmed and five sequences are identified in this paper by comprehensive analysis of seismic profiles,well logs and cores data.It is found that there is not any unconformity surface between Member 1and Member 2of Shahejie Formation,so they form the highstand system tract and lowstand-transgressive system tract of the sequence respectively.SQs3-1(the upper submember of Member 3)is nearly denudated in uplift area and widely distributed in the depression zone.All kinds of sedimentary facies have been recognized in the study area,including the fan delta system,braided delta system,nearshore subaqueous fan system and beach-bar system.The sedimentary system distribution is controlled by syndepositional fault,paleo-uplift and depression.The favorable sand bodies in the study area consist of those developed in the lowstand system tract at the edge of the paleouplift,deep water gravity flow sand in the center of the sub-sag and carbonate in the upper part of the paleouplift.With the underlying massive dark mudstone and shale in the third sequence of Shahejie Formation and the overlying pelolithic layer of the first sequence of Shahejie Formation,they can form good reservoir-cap assemblages and form litho-stratigraphic traps in the uplift,sub-sag,fault slope break and the gentle slope belt.更多还原