针对东营凹陷民丰地区古近系沙四段—沙三中亚段砂砾岩扇体类型认识的不统一,在工区26口取心井岩心观察和描述的基础上,结合地震、测井、录井及沉积物粒度特征等资料,对民丰地区沙四段—沙三中亚段近岸水下扇、扇三角洲及深水浊积扇等砂砾岩扇体的沉积特征进行了系统研究。结果表明,民丰地区沙四下亚段底部和沙三中亚段主要发育扇三角洲,沙四下亚段中上部、沙四上亚段和沙三下亚段主要发育近岸水下扇,深水浊积扇在各个时期均有发育,但规模较小。在识别不同层段砂砾岩扇体类型的基础上,综合民丰地区各时期构造活动特征、边界断层形态、气候条件、水体深度及湖盆的"敞-闭"状态等,分析了不同时期主要沉积相的沉积演化及分布特征。以此为基础,建立了断陷湖盆演化过程中"板式高角度断层-铲式高角度断层"继承性控制的陡坡带砂砾岩扇体的沉积演化模式,旨在对类似地区的油气勘探有所裨益。
No consensus has been reached on the types of sandy conglomerate fans in the 4th-middle 3rd members of Shahejie Formation in Minfeng area.Based on observation and description of cores from 26 wells and in combination with seismic data,logging data,and grain size characteristics,this paper systematically studied the sedimentary characteristics of sandy conglomerate fans,including nearshore subaqueous fans,fan deltas and deep water turbidite fans in the 4th-middle 3rd members of Shahejie Formation in Minfeng area.Fan deltas dominate the bottom of the lower 4th member and middle 3rd member of Shahejie Formation,while the nearshore subaqueous fans are predominant in the middle to upper part of the lower 4th member,the upper 4th member and the lower 3rd member of Shahejie Formation.Deep water turbidite fans exist in each interval,but their scales are small.On the basis of identifying the types of sandy conglomerate fans in different intervals,we analyzed the synsedimentary tectonic activity,the geometry of boundary fault,paleoclimate,water depth and the close and open of lake basin,and determined the evolution and distribution characteristics of the main sedimentary facies in different periods.Based on these studies,this paper puts forward a sedimentary evolution model for the sandy conglomerate fans in the steep-slope zone of rifted lacustrine basin under the successive controls of the'high angle plate fault-high angle listric fault',offering an appliccable instruction for oil and gas exploration in similar area.