以147口探井、300口开发井资料为基础,并重点结合25口取心井的岩石学特征及地震反演分析,对松辽盆地四方坨子地区泉头组四段—嫩江组三段开展层序地层划分及沉积演化规律研究.结果表明,泉四段—嫩江组地层可划分为3个Ⅱ级层序、7个Ⅲ级层序和21个Ⅳ级层序.在层序演化背景下,泉四段沉积期发育曲流河三角洲—滨浅湖沉积环境,青山口—嫩江组沉积期发育辫状河三角洲—滨浅湖—半深湖—深湖沉积环境.这一过程中,受沉积基准面升降、燕山期全盆左旋走滑和海侵作用的共同影响,沉积物源发生白城水系—英台水系—讷河水系的变化,沉积中心由齐家古龙凹陷向三肇凹陷迁移,突出表现为三角洲朵体轴向发生SW-NW-NE的顺时针旋转,以及青一段和嫩二段两期最大湖泛面的发育.基于上述沉积认识,提出了低幅构造脊聚集油气与湖泛期沉积寻找页岩油气资源的新思路.%The sequence stratigraphy and sedimentary evolution from the 4th member of Quantou Formation to the 3rd member of Nenjiang Formation in Sifangtuozi area of the Songliao Basin were studied based on data collected from 147 exploration wells, 300 development wells and 25 cored wells. Research shows that by analyzing petrology, sedimentary structures and seismic inversions, the targeted strata can be classified into three second order sequences, seven third order sequences and twenty?one fourth order sequences. Under the sequence framework, meandering river deltas and shallow lakes were developed when the 4th member of Quantou Formation was deposited, and braided river deltas, shallow, semi?deep and deep lakes were developed when the Qingshankou and Nenjiang formations were deposited. In this process, the changing of base level, the left?lateral slip of Yanshan Movement and the transgression jointly contributed to the results, including the provenance changing from Baicheng to Yingtai, and then to Nehe drainages. In addition, the depocenter migrated from the Qijia Sag to the Sanzhao Sag, which highlighted the deltaic cycle in a direction of SW-NW-NE and the occurrences of maximum flooding surfaces in the 1st member of Qingshankou Formation and the 2nd member of Nenjiang Formation. We recommend looking for oil and gas on low?scoped ridges and shale resources on MFSs.
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