摘要：
The deep oil and gas exploration potential of the Songzhan region in the northern part of the Xujiaweizi fault depression of Songliao basin is huge and can be used as an alternative field for deep exploration.In this paper, the Shahezi Formation in Dashen2 wellblock of Songzhan region is studied.By integrating data of core, well logging, mud logging and 3Dseismic survey, the sequence stratigraphy division and types of sedimentary facies analysis are carried out, and the characteristics of sedimentary evolution were further analyzed and the sedimentary facies model was established.The results show that the Shahezi Formation in the Dashen2 wellblock can be divided into one second-order sequence and four third-order sequences.There are mainly four types of sedimentary facies developed within the thirdorder sequence, including braided delta, fan delta, lacustrine and volcanic rock.The sedimentary facies are obviously distinct from east to west.The sedimentary process of the Shahezi Formation in the Dashen2 wellblock of Songzhan region is controlled by the boundary fault of the basin.Under the continuous activity of the Xuxi boundary fault, the sedimentation range is expanding, the fan delta migrates to the Xuxi fault zone, the braided delta extends to the eastern part of the fault depression, and the sedimentation range of shallow lacustrine reaches the maximum in the Sq4 period, which indicates that the Shahezi Formation is characterized by typical fault basin sediment.The research results in this paper can provide a certain geological basis for oil and gas exploration in this region and similar small-scale fault basins.%松辽盆地徐家围子断陷北部宋站地区深层油气勘探潜力巨大, 可作为深部勘探的备选领域.以宋站地区达深2井区沙河子组为研究对象, 综合运用岩心、测井与录井以及三维地震等资料, 进行了层序地层划分与沉积相类型分析, 进一步分析了沉积演化特征, 建立了沉积相模式.研究结果表明, 达深2井区沙河子组可划分为1个二级层序和4个三级层序, 在三级层序内部主要发育辫状河三角洲、扇三角洲、湖泊、火山碎屑岩等4种沉积相类型, 沉积相带东西分异明显.宋站地区达深2井区沙河子组沉积过程受到盆地边界断裂的控制, 在徐西控陷断裂的持续活动下, 沉积范围不断扩大, 扇三角洲向徐西断裂带迁移, 辫状河三角洲向断陷东部扩展, 浅湖沉积在Sq4时期范围达到最大, 表明沙河子组具有典型的断陷湖盆沉积特征.本文研究成果可为该地区及类似小型断陷湖盆的油气勘探提供一定的地质依据.
