东营凹陷沙三中亚段东营三角洲沉积期次成因及对含油性的影响

根据岩性组合变化、测井曲线叠加样式及地震反射特征，将东营三角洲沙三中亚段划分为八个期次，准层序组PS8~PS1，各期次间沉积小型湖泛泥岩楔。结合岩心及测录井沉积相分析，认为研究区发育三角洲-重力流-湖泊沉积体系。东南部主要发育三角洲分流河道、河口坝、席状砂，西北部发育与三角洲前缘滑塌相伴生的坡移堆积体、滑塌浊积岩和远源浊积岩。准层序组PS8~PS1，活动三角洲经历了由南至北的迁移演化过程。当波浪与河流能量能够抗衡并往复运动时，形成厚度较大的三角洲楔状体叠加区，沉积席状砂和河口坝砂体。受湖平面变化、构造沉降及沉积物供给速率的影响，湖退体系域早期PS7~PS4重力流砂体含油丰富，而浅水区准层序组界线附近的席状砂和河口坝由于临近具有侧向封堵及局部盖层作用的泥岩楔及沼泽沉积，其含油性也较好。

Origin of Depositional Cycles and Their Influence on Oil-bearing Sandstone of Dongying Delta in Mid-Es3, Dongying Depression

Based on lithology combination, logging curves stacking pattern and seismic reflection characteristics, this article divides Dongying delta into eight cycles, parasequence set 8 to parasequence set 1(PS8~PS1). Between two cycles mudstone wedge deposits for small scale lake-flooding. According to core observation and logging analysis of sedimentary facies, it indicates that delta-gravity flow-lacustrine depositional system develops in the study area. Delta distributary channel, mouth bar and sheet sands deposits in southeast, and slide congeries, slump turbidite, distal turbidite associated with delta front slump deposits in northwest. From PS8 to PS1,the active delta migrates from south to north. When wave force and river energy are well matched and alternating motion, the sheet sands and mouth bars deposit, forming large thickness of delta progradation wedge. Under the effect of lake level change, tectonic subsidence rate and sediment supply rate, in early regressive system tract PS7~PS4, the gravity flow sand bodies are rich in oil, and the sheet sands and mouth bars, depositing near the parasequence set boundary are also well oil-bearing, because of close to mudstone wedge and swamp deposition which are lateral sealing and local cap rock.