摘要:
运用高分辨率层序地层学原理将准噶尔盆地莫北凸起侏罗系三工河组划分为10个短期基准面旋回、2个中期基准面旋回。按照短期基准面旋回期次分析了该区沉积演化特征,在三工河组沉积期,研究区经历了辫状河三角洲前缘、曲流河三角洲前缘及滨浅湖的交替演化过程。不同的演化期,其微相构成具有很大的差别,辫状河三角洲前缘沉积主要由辫状河水下分流河道微相及河道间微相构成,河口砂坝及远砂坝不发育;曲流河三角洲前缘沉积微相有曲流河水下分流河道、支流间湾、河口坝、远砂坝及席状砂,以水下分流河道微相为主,河口坝较发育,远砂坝、席状砂次之;滨浅湖沉积微相由砂泥坪及滩坝构成。通过分析认为,在中期基准面下降到上升的转换位置,辫状河水下分流河道叠置连通广泛分布,为本区最有利的构造油气藏储集砂体;中期基准面上升和下降的中期,曲流河三角洲前缘水下分流河道及河口坝砂体发育,孤立状分布,为形成岩性油气藏的有利储集砂体。
Abstract:
Based on the high-resolution stratigraphic principles, the Jurassic Sangonghe Formation is divided into 10 short-term base-level cycles and 2 middle-term base-level cycles. The analysis of sedimentary evolution was carried out based on the short-term base-level cycles. In the period of Sangonghe Formation sedimentation, the 3 kinds of sedimentary conditions (braded-river delta front, meandering-river delta front and shore shallow lacustrine) occurred alternately. In the different sub-periods, there are different microfacies. The microfacies of braded-river delta front mainly include braded sub-water channels and interchannels, debouch bars and mat-shape sands scarcely occur. Meandering-river delta front mainly consists of sub-water meandering branch channels, interchannels, debouch bars, far bars and mat-shape sands; While shore shallow lacustrine consists of mudflats and bank bars. The study result shows in braided-river delta front sub-water channels that superimpose and distribute widely in succession, are favorable reservoirs for structural oil pools and exist in change place of middle base-level from descending to ascending. In center of middle base-level ascending and descending, sub-water channels and debouch bars that distribute isolatedly, are the main microfacies in meandering-river delta fronts. They are advantageous reservoirs for lithologic oil pools.
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