埕北凹陷古近系构造对沉积的控制作用

Development of structure and its control on sedimentary system of Paleogene in Chengbei sag

利用埕北凹陷钻井、录井、测井、地震资料等,分析研究区古近系构造结构特征,恢复古近纪构造演化,划分沉积相类型,研究沉积体系的时空展布规律,明确古近系构造对沉积的控制作用。结果表明:埕北凹陷古近系发育的NW向断裂控制研究区凸凹格局,NE、NEE向断裂改造NW向构造格局。埕北凹陷古近纪构造演化分为三个阶段,继承断陷期(Ek-Es4)表现为"窄盆、浅水"环境,主要发育扇三角洲沉积;断陷扩张期(Es3)表现为"深盆、深水"环境,以发育半深湖—深湖沉积为主;断—坳转换(Es2-Ed)早期表现为"广盆、深水"环境,以发育半深湖—深湖沉积为主,晚期表现为"广盆、浅水"环境,主要发育辫状河三角洲与曲流河三角洲沉积。研究区古近系发育陡坡断裂坡折带、缓坡断裂坡折带及洼陷边缘型坡折带三种类型,其中陡坡断裂坡折带主要发育扇三角洲沉积,缓坡断裂坡折带主要发育辫状河三角洲与曲流河三角洲沉积,洼陷边缘型坡折带主要发育巨厚的湖相沉积及少量湖底扇沉积。该结果为研究区古近系油气勘探提供指导。

Using the drilling,logging,well logging,seismic data and other geological data of Paleogene in Chengbei sag,analyzing the structure characteristics of Paleogene in study area,dividing the types of sedimentary facies and studying the distribution rule of sedimentary system,the paper reveals the controlling of structure on the sedimentary system,which guides oil and gas exploration of Paleogene in study area.The result shows the NW faults control the structure framework of the Chengbei sag,and the NE and NEE faults alter the NW structure framework.Chengbei sag in Paleogene can be divided into three evolution stages,and the inherited faulted stage(Ek-Es4)is'narrow basin,shallow water'sedimentary environment,which mainly forms fan delta sediments.Faulted expansion stage(Es3)is'wide basin,deep water',which mainly forms semi-deep and deep lacustrine sediments;the fault-sag transition stage(Es2-Ed)also includes the early fault-sag transition stage and the late fault-sag transition stage,and the former one is'wide basin,deep water',which also forms semi-deep and deep lacustrine sediments,but the latter one is'wide basin,shallow water',which mainly forms braided river delta and mender river delta sediments.The study area possesses three kinds of break-slope,which are steep slope faulted break-slope,gentle slope faulted break-slope and subsagmargin break-slope,and these three break-slopes mainly control the forming of fan delta sediments,braided river delta and mender river delta sediments,and semi-deep and deep lacustrine sediments and sublacustrine fan sediments respectively.