准噶尔盆地东部芦草沟组层序地层格架与沉积充填模式

Sequence stratigraphic framework and sedimentary filling model of Lucaogou Formation in eastern Junggar Basin

准噶尔盆地东部克拉美丽山山前凹陷中二叠统平地泉组相当于博格达山山前凹陷的芦草沟组与红雁池组,芦草沟组与平地泉组均为重要的烃源岩层系,尚未建立芦草沟组与平地泉组的等时地层格架,制约了烃源岩在横向和纵向上分布范围的落实。通过系统分析井-震、露头及地化等资料,划分了芦草沟组层序地层单元,明确了与平地泉组的地层对应关系,建立了准噶尔盆地东部芦草沟组沉积充填模式。研究结果表明:博格达山周缘中二叠统芦草沟组及红雁池组各为一个三级层序,分别对应平地泉组下部的三级层序1与上部的三级层序2。芦草沟组(层序1)发育低位域、湖侵域与高位域,低位域以扇三角洲、三角洲与滨浅湖沉积为主,半深湖-深湖亚相仅分布在博格达地区;湖侵域半深湖-深湖亚相在各凹陷分布范围达到最大;高位域扇三角洲、三角洲及浊积扇砂体规模增大,半深湖-深湖亚相分布范围减小。芦草沟组湖侵域与高位域沉积时期,半深湖-深湖亚相发育了优质烃源岩,与高位域各类型砂体构成良好的生储组合。芦草沟组高位域为准噶尔盆地东部中二叠统较有利的勘探层系。

The Middle Permian Pingdiquan Formation in the piedmont depression of Kelameili Mountain in eastern Junggar Basin is equivalent to Lucaogou Formation and Hongyanchi Formation in the piedmont depression of Bogda Mountain.Lu⁃caogou Formation and Pingdiquan Formation are important series of strata with source rocks.The isochronous stratigraphic framework of Lucaogou Formation and Pingdiquan Formation has not been established,which affects the distribution range of source rocks in horizontal and vertical directions.According to the systematic analysis of well seismic,outcrop and geo⁃chemical data,this paper divides the sequence stratigraphic units of Lucaogou Formation and clarifies the corresponding re⁃lationships with Pingdiquan Formation.Moreover,the paper establishes the sedimentary filling models of Lucaogou Forma⁃tion in eastern Junggar Basin.The results show that the middle Permian Lucaogou Formation and Hongyanchi Formation on the periphery of Bogda Mountain are both third-order sequences,respectively corresponding to the third-order sequence1 at the lower part of Pingdiquan Formation and the third-order sequence 2 at the upper part.Lucaogou Formation(Sequence1)develops lowstand,transgressive and highstand system tracts.The lowstand system tract is dominated by fan delta,delta and shore-shallow lake deposits,and the semi-deep lake-deep lake facies is only distributed in Bogda area.The distribution ranges of semi-deep lake-deep lake facies in the transgressive system tract reach the maximum in each sag.The scales of fan delta,delta and turbidite fan sand bodies in the highstand system tract increase,and the distribution rang⁃es of semi-deep lake-deep lake facies decreases.During the sedimentary period of transgressive and highstand system tracts in Lucaogou Formation,the semi-deep lake-deep lake facies developed high-quality source rocks,which formed a good source-reservoir assemblage with various types of sand bodies in the highstand system tract.The highstand system tract of Lucaogou Formation is favorable exploration strata of Middle Permian in eastern Junggar Basin.