【摘要】 应用沉积学和层序地层学的原理和方法,利用地震、钻井、岩心等资料,结合盆地区域构造演化特征,建立了海拉尔盆地贝尔凹陷贝西地区南屯组层序地层格架,将南屯组划分为1个超层序、4个三级层序、11个体系域。在层序格架内共识别出扇三角洲、辫状河三角洲、湖底扇、湖泊4种主要沉积相类型及8种亚相类型。南屯组沉积时期区内经历了初始沉降-快速沉降-沉降减弱-萎缩的构造演化过程,并形成与其对应的4个三级层序:SQ1沉积时期,研究区为分割的断陷盆地,湖盆规模较小,主要发育扇(辫状河)三角洲;SQ2沉积时期,湖盆规模迅速增大,统一的湖盆基本形成,沉积格局与SQ1时期相似,但有所不同的是区内西南缘出现物源供给,形成扇三角洲沉积;SQ3沉积时期,湖盆规模最大,区内各个物源方向的扇(辫状河)三角洲沉积规模明显减小,湖底扇及滑塌浊积体等重力流深水沉积相对发育;SQ4沉积时期,湖盆萎缩,湖盆规模迅速减小,同时东南部物源供给不足,造成东南部辫状河三角洲沉积几乎消失。生储盖组合及成藏条件综合分析表明:SQ2、SQ3低位体系域及高位体系域发育优质储层,并由于紧邻规模较大的烃源岩,在邻近断裂发育地区易形成断块圈闭及断背斜圈闭;在斜坡地区和缓坡带可形成不整合面作为遮挡的不整合-岩性圈闭及以各类砂体作为储集空间的地层超覆圈闭。更多还原

【Abstract】 Seismic data,logging,cores,connecting with the characteristic of structure evolution are used to establish the sequence stratigraphic framework of the Nantun Formation in the western area of Beier depression,Hailaer basin.The Nantun Formation in the study area finally can be divided into one supersequence,four three-order sequences and eleven systems tracts.There are four facies including fan delta,braid river delta,sublacustrine fan and lake,and eight subfacies can be identified in the sequence stratigraphic framework of the Nantun Formation.During the depositing period of Nantun Formation,the study area experienced the tectonic evolution process which experienced from initial subsidence state to a rapid subsidence stage,then to a subsidence decrease stage,and to a shrink stage finally,which respectively corresponded with four three-order sequences.In the depositing period of sequence SQ1,this area was a separated rifted basin,fan delta mainly formed in the northwest and northeast of the area,and braid river delta mainly formed in the southeast of the area;at this time,the area of lake basin is also small.During the depositing period of sequence SQ2,the area of lake basin expanded rapidly with the lake level rising and finally formed a unified lake basin;the sedimentary framework is similar to the depositing period of sequence SQ1,but the difference is that in the southwest of this area,a provenance appeared and then fan delta sedimentary began.In the depositing period of sequence SQ3,the lake-basin area reached to the largest scale;the area scale of all fan(braid river) deltas from corresponding respective provenance direction obviously reduced and deep water sediments including sublacustrine fan and fluxoturbidite formed relatively more.In the depositing period of sequence SQ4,the lake basin area scale decrease rapidly;meanwhile,the sediment from the southeastern provenance supplied not enough to the basin,leading to the braid river delta in the southeast of centre almost disappear at that time.On the basis of comprehensive research on the reservoir-cap combination distribution and the conditions of the migration and accumulation of oil and gas,it shows that most favorable reservoir-cap combination formed in the lowstand system tracts and the highstand system tracts of sequence SQ2 and SQ3 of the Nantun Formation.These fault development areas are prone to form block fault traps and fault anticline traps because of having preferable reservoir rock and being near the hydrocarbon source rock.The slope and ramp can form unconformity-lithologic traps by the unconformity as the barrier bed and the stratigraphic overlap traps by all kinds of sand bodies as the reservoirs.更多还原