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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.
According to the data of comprehensive earthquakes, logs and cores, there is a complete stratigraphic sequence of the Paleogene Shahejie Formation in the northwestern Liaoning depression, which can be divided into five third-order sequences. There is no unconformity between the Sha-1 and Sha-2 segments The upper sedimentary system of SQs3-1 (Upper Triassic) was eroded in the opposite uplift but developed well in the depression.The major sedimentary systems developed in the Shahejie Formation include fan delta, braided river delta, nearshore subaerial fan, The shallow shoal dam and so on, its distribution is restricted by the syndepositional faults, secondary paleohighs and paleo-depressions.The favorable reservoirs in the study area include the sand body distributed in the lowstand system tract of the paleo-uplift margin, the central part of the depression Of the deep-water gravity flow sand body, the paleo-uplift of carbonate rocks, etc. They formed a good reservoir-cap assemblage with a large set of dark mudstone and overlying sand-first argillaceous layer in the lower part of Shahejie Formation, Uplift margins, sub-subsidence belts, fault-break belts and gentle slope edges form lithologic stratigraphic traps.