准噶尔盆地阜东斜坡区侏罗系层序地层及沉积体系展布

Sequence stratigraphy and sedimentary system distribution of the Jurassic in Fudong slope area,Junggar basin

为认识准噶尔盆地阜东斜坡区侏罗系层序地层及沉积体系展布,根据层序地层学理论,综合地震、测井、录井及岩心资料,并结合各层序井—震联合标定,对准噶尔盆地阜东斜坡区侏罗系进行层序地层划分,建立层序地层格架。结果表明:在该地区共识别3个二级层序界面和5个三级层序界面,划分7个三级层序;二级层序界面对应侏罗系顶、底界面及西山窑组沉积末期;三级层序自下而上对应八道湾组下段、八道湾组上段、三工河组、西山窑组、头屯河组、齐古组及喀拉扎组地层;根据层序地层结构特征,将7个三级层序分为二分层序、三分层序和四分层序3种类型。该地区沉积相类型主要包括扇三角洲、辫状河三角洲、曲流河三角洲、辫状河—曲流河和湖泊相,其中辫状河三角洲相是主要沉积相类型。SQ1—SQ6层序格架内,沉积相演化依次表现为扇三角洲(八道湾组,即SQ1—SQ2)—辫状河三角洲(三工河组,即SQ3)—曲流河三角洲(西山窑组,即SQ4)—辫状河—曲流河(头屯河组,即SQ5)—曲流河(齐古组,即SQ6)的演化序列,整体上侏罗系形成一套正旋回,粒度自下而上由粗逐渐变细。综合分析各层序地层特征及沉积体系展布规律,为寻找优质储集砂体、确定有利勘探方向提供重要证据。

In order to further understand sequence stratigraphy and the sedimentary system of distribution of the Jurassic in Fudong slope area of Junggar basin,based on the sequence stratigraphic theory and analysis of seismic and well logging information and mud logging information and core data,combined with well-seismic calibration of each sequence,the sequence of the Jurassic in Fudong slope area of Junggar basin is classified,the strata framework of sequence is defined and established.The results show that three second-order sequence boundaries,five third-order sequence boundaries and seven thirdorder sequences are identified in the region.The second-order sequence boundaries are the top boundary of Jurassic,the bottom boundary of Jurassic as well as the end of Xishanyao,third-order sequence corresponds to the Badaowan group(under),Badaowan group(above),Sangonghe group,Xishanyao,Toutunhe group,Qigu group and Kalazha group from bottom to top.According to the characteristics of sequence stratigraphic structure,the seven third-order sequence can be classified into three types:two-divided sequence,three-divided sequence and four-divided sequence.This area mainly includes fan delta facies,braided river delta facies,meandering delta facies,braided stream-meandering river and lake facies.For SQ1-SQ6 sequence,the evolution of sedimentary facies is fan delta facies(Badaowan group,SQ1-SQ2)-braided river delta facies(Sangonghe group,SQ3)-meandering delta facies(Xishanyao group,SQ4)-braided stream-meandering river(Toutunhe group,SQ5)-meandering river(Qigu group,SQ6).Form a positive cycle in Jurassic,particle size changed from coarse into fine granule from the bottom up.Analyzing comprehensively the characteristics of sequence stratigraphy and sedimentary system distribution law,the theoretical foundation will be provided in order to look for high quality reservoir sand bodies and determine the favorable exploration direction.