摘要:
开鲁盆地陆西凹陷是一个典型的中生代单断箕状盆地,充填了厚达3000余米的下白垩统并表现出良好的沉积旋回特征.依据钻井取心资料、测井和地震资料以及分析化验资料,将下白垩统划分成周期为4～6 Ma的3个沉积层序并总结了层序边界和体系域边界的识别标志.考虑箕状盆地结构、构造活动特征以及沉积物供源方式,分别论述了盆地陡坡、深洼和缓坡的层序地层样式,指出不同地形区的层序地层叠置样式主控因素是有差异的.依据盆地缓坡地形变化带,可以将一个沉积层序细分成低位、湖侵和高位体系域.研究区层序Ⅲ高位和低位体系域富含油气资源,是今后寻找隐蔽圈闭的主要层段。
Abstract:
Luxi depression is a typicaI Mesozoic fauIted-down basin with more than 3 000 m Iower Cretaceous in thickness.The fiIIings of Iower Cretaceous were deposited in semi-saItwater Iacustrine and were characterized by cIastic cycIes in verticaI profiIe. According to the characteristics of seguence boundary and fIooding surface from core,weII Iogging,seismic data and resuIts of exampIe anaIysis in Iaboratory,the Iower Cretaceous in the study area couId be divided into three depositionaI seguences with period 4 ~ 6 Ma. There was a speciaI topographic break on gentIe sIope in Luxi depression during Cretaceous；so,a seguence couId be made up of Iowstand,transgressive and highstand systems tracts iike Vaii's marine seguence modei. Because of the difference of basin texture,fauit activity and materiai suppiy,the main controiied factors of seguence styie were different in steep siope,deep-water area and gentie siope. The major controiied factor of seguence styie on steep siope was fauit activity and materiai suppiy,and the nearshore subagueous fan was main sedimentary type；the factor controiied seguence styie in deep water area was reiative change of iake ievei,the sedimentary facies was characteristic of shaiiow-deep iake；the factor controiied seguence styie on gentie siope was reiative change of iake ievei and materiai suppiy,fan-deita or river-dominated deita was major sedimentary type. Therefore,the seguence modeis were estabiished separateiy on steep siope deep-water area and gentie siope. A seguence was made up of iowstand,transgressive and highstand systems tracts with topographic break on gentie siope of Luxi depression. Lastiy,authors anaiyzed the condition of hydrocarbon accumuiation in different seguence framework, and pointed out that the iowstand and highstand systems tracts of seguence Ⅲ were rich in hydrocarbon resource,and were the main section for finding new hidden traps.
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