松辽盆地北部西斜坡青二段至姚一段四级层序格架内沉积微相分布

Sedimentary microfacies distribution under the 4th-order sequence stratigraphic framework of the member 2 of Qingshakou formation to the member 1 of Yaojia formation in west slope of the northern part of Songliao basin

以松辽盆地北部西斜坡青山口组二段至姚家组一段高频层序地层为研究对象,研究各体系域内沉积体系充填类型和展布规律,利用地震、测井、岩心和古生物资料,建立松辽盆地西斜坡中青二段至姚一段四级层序格架;分析四级层序格架内沉积微相类型、沉积体形态及规模,确定沉积微相时空分布和演化特征。结果表明:青山口组二段划分为2个四级层序(Cg4、Cg3),青山口组三段划分为3个四级层序(Cg2、Cg1、Cg0),姚家组一段划分为1个四级层序(Cp1),各四级层序内均能识别出相应级次的湖泊扩张体系域和湖泊收缩体系域。研究区主要发育三角洲前缘河口坝、远砂坝、滨浅湖混合滩、砂滩和钙质浅滩沉积微相,富砂的三角洲前缘、滨浅湖砂质滩坝微相与富泥的滨浅湖混合滩微相在剖面上形成储盖组合;平面上,来源于四个物源方向的三角洲沉积体在青山口组二段的各体系域沉积时期逐渐向湖推进,与滨浅湖混合滩、泥滩微相共存,并新发育西北物源三角洲;青山口组三段沉积阶段三角洲沉积体规模明显缩小,以发育滨浅湖钙质浅滩微相为特征,Cp1时期三角洲再次向湖迁移,滨浅湖不断萎缩。该研究结果为研究区地层—岩性油气藏预测、评价提供依据。

Based on high frequency sequence stratigraphy of the member 2of Qingshankou formation to the member 1of Yaojia formation in the west clinoform of northern Songliao basin,the distribution characteristics and filling types of sedimentary system in each system tract was discussed.The framework of 4th-order sequence was reconstructed by comprehensive utilization of eismic,logging and coredata of the middle oil-bearing beds in the west clinoform of Songliao basin,spital distribution and evolutional characteristics of sedimentrary microfacies was dicussed based on the analysis of types,forms and distribution scale of sedimentary bodies.The results shows that The member 2of Qingshankou formation was divided into two 4th-order sequeces(Cg4and Cg3),The member 3of Qingshankou formation was divided into three 4th-order sequeces(Cg2,Cg1 and Cg0)and the member 1of Yaojia formation only devoloped one 4th-order sequeces(Cp1).Each of the 4th-order sequence was divided into lake expanding system tract and lake shrinking system tract.In the profile section,sand-rich delta front and shore-shallow lacustrine sandy beach-bars mostly developed nearby the 3rd or 4th-order sequence boundary,while the main sendimentary microfacies was the mud-rich shore-shallow lacustrine mixed beach which developed nearby the maximum flooding surfaces of the 4th-order sequence.In the plane,the characteristics of microfacies distribution of different 4th sequences system tracts has certain inheritance,and has the obvious difference.This article will provide the basis for identification of stratigraphic and lithologic reservoirs and determination the favorable exploration direction of research area.