二连盆地下白垩统层序地层及砂体分布垂向序列

二连盆地是在海西期地槽褶皱基底上发育起来的早白垩世断陷湖泊群,具有潮盆潮侵规模较小、气候条件干燥、湖水咸化、沉积旋回单一、多物源、近物源和粗碎屑等沉积特征,以及发育岩性地层油气藏为主的油气分布特点。本文通过对巴音教兰、乌里雅斯太、吉尔嘎朗图和赛汉塔拉等凹陷层序地层分析,建立了二连盆地下白垩统层序地层综合剖面,并总结了三级层序框架内砂体分布的垂向序列。主要的结论为：其一,受三期幕式话动影响,断陷形成了3个大的沉积旋回和3个区域不整合面,构成了下白垩统3个二级层序；其二,受断陷内翘倾和块断等构造活动的控制,以及三级气候旋回和物源供给因素的影响,下白垩统划分出6个三缓层序；其三,在单断断陷湖盆中,湖泊阶段的早、晚期由于凹陷边界断层活动较弱,断面较缓,陡坡可以发育扇三角洲,在湖泊阶段的中期主要为水下扇砂砾岩体,并在洼槽区发育浊积扇。在整个湖泊阶段,缓坡的扇三角洲和辫状河三角洲砂体交替出现。

Sequence Stratigraphy and Vertical Sequence of Sandbodies Distribution in Lower Cretaceous Formations in Erlian Basin

Erlian basin is a rift lacustrine basin developed on the Hercynian geosyncline folded base in Early Cretaceous, is featured by simple sedimentary feature, depositional cycle, small lacustrine transgressive, dry climate, salinization lacustrine water and multi-and- near sources. On the basis of sequence stratigraphy analysis of Bayindulan sag, Wuliyasitai depression, Jiergalangtu sag and Saihantala sag, the integrated sequence stratigraphy section of lower Cretaceous has been established and the vertical sequence of sandbodies distribution in three-order sequence has been concluded. The main conclusions are as follows: Firstly, under the influence of three phases of episodic activities, three two-order sequences is composed of three depositional cycles and three regional unconformities; Secondly, under the control of structure activities such as fault-block activities and the influence of three-order climate cycles and source recharge , lower Cretaceous can be divided into six three-order sequence; Thirdly, because fault activities is weak and fault slope is gently , fan deltas exist in steep slopes in early and later stages and subaqueous fans exist and turbidite fans exist in troughs in middle stage. Fan deltas distributed in gently slopes and braided river deltas develop alternately in all stages.