为了阐明二连盆地洪浩尔舒特凹陷重点区块沉积砂体分布特征以及更好地指导油气精细勘探,在层序地层学和现代沉积学理论指导下,依据地震反射终止关系、岩性、沉积构造及其序列以及测井相特征,将二连盆地洪浩尔舒特凹陷白垩系阿尔善组划分为包含低位、湖侵及高位体系域的一个完整三级层序.高位体系域主力产油层段可划分为3个准层序组(砂组)和10个准层序(小层),且每个小层均发育了近岸水下扇和辫状河三角洲.近岸水下扇岩性为块状砂砾岩,发育块状和递变层理、叠覆冲刷,与暗色泥岩伴生构成间断正韵律;辫状河三角洲岩性为发育中型、大型楔状交错层理及冲刷面的砂岩,呈间断正韵律.随着湖平面升降,近岸水下扇和辫状河三角洲发生进积和退积,其中阿尔善组Ⅱ砂组沉积时期物源供给充足,形成规模较大的砂体,因此Ⅱ砂组可作为洪10区块阿尔善组的重点勘探层段.%In order to demonstrate the distribution of sedimentary sandbodies and guide fine hydrocarbon explora-tion in key areas in Honghaoershute Sag,Erlian Basin,under the guidance of the theories of sequence stratigra-phy and sediemntology,based on the seismic reflection termination,lithology,sedimentary structure and well log facies,the Cretaceous A'ershan Formation was divided into one third-order sequence including lowstand sys-tems tract (LST),transgressive systems tract (TST) and highstand systems tract (HST) in Honghaoershute Sag.The oil producing interval of HST could be divided into three parasequence sets (sand groups) and ten parase-quences (sublayers),and nearshore subaqueous fan and braided delta are developed.The nearshore subaqueous fans are characterized by coarse sandy conglomerate with massive and grading beddings,scour,and interbeded with dark mudstone;while the braided deltas developed sandstone with middle-large wedge-shaped cross bed-ding,scour surface and discontinuous rhythm.The nearshore subaqueous fan and braided delta will prograde to-ward central lake or retrograde toward parent rock region following the lake level up or down.Large sandbodies are developed in sand group Ⅱ of A'ershan Formation because of sufficient source supply,therefore,sand group Ⅱ can be taken as key strata for further exploration in Hong 10 block of Honghaoershute Sag.
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