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鄂尔多斯延长组湖盆为一大型的敞流湖盆.其充填演化与构造发育史、古气候演化史具有明显的一致性,可以划分为4个演化阶段,即湖盆形成及扩张期、鼎盛期、回返期、萎缩消亡期.在此过程中,湖盆经过四次明显湖进与湖退变化,但深湖中心变化不大,一直沿华池—宜君一带波动.在整个晚三叠世盆地盛衰演化过程中,深湖沉积体系主要为深水型三角洲及浊积扇体系,前者在深湖扩展早期的三角洲快速推进时期的陡岸斜坡区比较发育,并随着三角洲的推进逐渐从深水型向浅水台地型转变.后者在各个时期都有出现,按其沉积特征可分为两种浊积扇:坡移浊积扇相带发育相对齐全,垂向上多期互相叠加,可划分为:斜坡-槽道-内扇亚相、浊积水道、浊积水道间、浊积水道前缘-中扇亚相、外扇亚相和盆地平原亚相.滑塌浊积扇多呈透镜状夹于深湖亚相的深灰色泥岩中,相带分异不明显,仅可分为中心相和边缘相.两类浊积扇主要分布在盆地的近源斜坡带及远源末梢斜坡带.深湖沉积控制了烃原岩及有利生储盖组合分配.坡移浊积扇沉积厚度大,分布广,储集物性好,是深湖区岩性油藏勘探的主要目标.
The Ordos Yanhu Formation is a large open-stream lake basin, and its filling evolution, tectonic history and paleoclimate evolutionary history are obviously consistent and can be divided into four stages of evolution, ie, the formation and expansion of the lake basin, the peak period , The period of return and the period of shrinking and disappearing.During this process, the lake basin has undergone four obvious changes in lake and lake retreat, but the center of the lake has little change and fluctuates along the Huachi-Yijun area.During the late Triassic During the ebb and flow of the basin, the deep-lake sedimentary system is mainly composed of deep-water delta and turbidite fan systems. The former developed in the steep slope area during the early rapid delta advancement in the deep lake and developed gradually from the deep-water type Which changes to shallow water platform type.The latter appears in all periods and can be divided into two kinds of turbidite fans according to the sedimentary characteristics: the sloping turbidifolian facies belt is relatively complete in development, superimposed on each other in vertical direction and can be divided into: Slopes - channels - inner fan subphase, turbid water channel, turbid water channel, turbid water channel front - mid-fan subfacies, outer fan subfacies and basin plain subfacies. Lenticular sandwiched in deep-gray mudstone in the deep lake subfacies, facies belts There are two types of turbidite fans mainly distributed in the near-source slope zone and distal extremity slope zone in the basin, and the deep-lake sediments control the combination of hydrocarbon source rocks and favorable reservoirs and caprocks The sloping turbidite fan has the characteristics of large thickness, wide distribution and good reservoir properties, which are the main targets of lithologic reservoirs exploration in the deep lake area.