秦皇岛32-6油田北区新近系明化镇组下段复合砂体构型及控制因素

Composite sand body architecture and controlling factors of the lower Minghuazhen Formation of Neogene in northern Qinhuangdao 32-6 oilfield

通过测井、优势地震属性融合、频谱属性趋势分析等方法,对秦皇岛32-6油田北区新近系明化镇组下段Ⅱ油组(NmⅡ)复合砂体储层构型特征进行了研究,并厘清了基准面旋回对复合砂体构型的控制作用。研究结果表明:(1)秦皇岛32-6油田北区新近系明化镇组下段复合砂体主要为点坝-决口扇沉积,渗流屏障主要为河漫滩-废弃河道沉积,按测井相和砂体结构韵律划分内部结构,点坝砂体头部—中部为箱形,点坝尾部砂体为钟形,决口扇砂体主要为漏斗形,河漫滩和废弃河道主要表现为尖峰形和低幅齿形;复合砂体外部叠置样式包括孤立型、紧密侧叠型、疏散侧叠型和堆叠型。(2)研究区NmⅡ油组沉积早期,河道呈交织条带状分布,主要沉积点坝与决口扇,堆叠式和紧密侧叠型复合砂体广泛发育;沉积晚期河道演化为单一条带状,决口扇零星分布于河道凸岸,复合砂体规模变小,主要为疏散侧叠型和孤立型,河漫滩和废弃河道规模变大,成为复合砂体间的渗流屏障。(3)研究区长期—中期旋回中,构造活动等异旋回因素通过调整可容空间和沉积物供给,影响复合砂体外部形态和叠置样式;短期旋回通过控制沉积物类型和水动力等自旋回因素影响复合砂体内部结构。

Through logging,dominant seismic attribute fusion,spectrum attribute trend analysis and other methods,the reservoir architecture characteristics of the composite sand bodies in the second oil group(NmⅡ)of the lower Minghuazhen Formation of Neogene in northern Qinhuangdao 32-6 oilfield were studied,and the control effect of base-level cycle on the composite sand body architecture was clarified.The results shows that:(1)The composite sand bodies of the NmⅡ in northern Qinhuangdao 32-6 oilfield are mainly point bar and crevasse splay deposits,and the seepage barrier is mainly floodplain and abandoned channel deposits.According to logging facies and sand body structure rhythm,the internal structure of composite sand bodies is divided into box shape in the head and middle of point bar,bell shape in the end of point bar,funnel shape in crevasse splay,peak shape and low-amplitude tooth shape in floodplain and abandoned channel.The external stacking patterns of the composite sand bodies include isolated type,tight lateral stacking type,scattered lateral stacking type and stacking type.(2)In the early stage of NmⅡ,the intertwined channel mainly deposited point bar and crevasse splay.Sand bodies of tight side-stacking type and stacking type were widely developed.In the late stage of Nm Ⅱ,the channel evolved into single band shape,and the crevasse splay was sporadically distributed on the convex bank of the channel.The scale of the composite sand bodies became smaller,mainly scattered lateral stacking type and isolated type,and the floodplain and abandoned channel became the seepage barrier between the composite sand bodies.(3)In long-term to middle-term cycles in the study area,heterocyclic factors such as tectonic activities affect the external morphology and stacking of composite sand bodies by adjusting the accommodation space and sediment supply,while in short-term cycles,the internal structure of sand bodies is affected by autogenetic cycle such as sediment types and hydrodynamics.