分流砂坝型浅水三角洲储层构型研究

为了揭示分流砂坝型浅水三角洲储层分布特征及其内部结构，综合应用现代沉积、岩芯、测井和动态资料，根据构型层次分析理论，对渤海海域A油田NmⅡ-1小层进行了精细构型研究，建立了分流砂坝型浅水三角洲构型分级系统，阐明了其内部单砂体的空间配置关系。研究表明，分流砂坝为该类浅水三角洲的主要构型单元，其中，五级构型单元为同期分流砂坝复合体，四级构型单元为单一分流砂坝，三级构型单元为分流砂坝内部增生体。研究区主要发育泥岩、泥质粉砂岩和粉砂质泥岩3种单一期次砂体构型界面；单一成因分流砂坝长约600~1 300 m，宽约400~800 m，厚度约2.5~7.0 m；垂向上呈部分叠置、主体叠置和主体叠加3种接触样式，平面上呈孤立分布、边部侧向拼接和主体侧向拼接3种组合样式，总体呈"早期前积伴随侧向迁移-晚期逐渐超覆加积"式演化。分流砂坝内部发育3种不同成因类型的泥质夹层，其中，顺源为前积倾斜式夹层，垂直物源为侧迭式和垂积水平式夹层，侧迭式夹层发育于近端物源区，垂积水平式夹层发育于远端湖盆区；研究区夹层厚度一般在0.4~1.2 m，延伸多小于300 m。

Study on the Hierarchy of A Distributary-mouth Bar Type Shallow-water Delta Reservoir

To determine the distribution characteristics and internal structure of a distributary-mouth bar type shallow-water delta reservoir, this study integrated current sedimentation, rock core, well logging, and dynamic data and performed hierarchy analysis on the NmⅡ-1 layer of oilfield A in Bohai Sea. The study established a grading system for the hierarchy of the distributary-mouth bar type shallow-water delta and describes the spatial configuration among its internal single sandbodies. Distributary-mouth bars were identified as the main structural unit of this class of shallow-water deltas, of which the level 5 structural units are complexes formed from distributary-mouth bars of the same period, level 4 units are single distributary-mouth bars, and level 3 units are internal accretion bodies of the distributary-mouth bars. Three main types of single-phase sandbody structural interfaces were identified:mudstone, argillaceous siltstone, and silty mudstone. The length, width, and thickness of distributary-mouth bars of single origin are about 600~1 300 m, 400~800 m, and 2.5~7.0 m respectively, arranged vertically in partially overlapped, main-body overlapped and main-body superimposed configurations, and laterally in isolated, edge sideway joined and main-body sideway joined patterns. The overall evolution is "early foreset deposit with lateral migration-late gradual overlapping aggradations." Three mud interlayers of varied genesis developed in the distributary-mouth bars:foreset inclined layer along the source direction, sideway overlapped layer, and vertically accreted horizontal layer perpendicular to the source. The sideway overlapped layer developed in the proximity of the source, whereas the vertically accreted horizontal layer developed at the lake basin region to the far side. The interlayer thickness of the study area is generally 0.4~1.2 m, with extension less than 300 m.