曲流河与辫状河沉积砂体连通模式及开发特征——以渤海地区秦皇岛32-6油田为例

Sandbody interconnectivity architecture and development characteristics of meandering river and braided river deposits——a case study of Qinhuangdao 32-6Oilfield,Bohai area

渤海地区新近系河流沉积体系发育,而不同类型的河流砂体内部连通模式和开发特征表现出较大的差异。依据岩心观察,充分利用密井网资料,采用层次分析法,详细解剖了渤海地区秦皇岛32-6油田新近系明化镇组高弯度曲流河、砂质辫状河砂体的内部结构,建立了其连通模式。曲流河点砂坝内部一般由30～200个侧积体构成,单个侧积体厚度为1～3m,砂体上部4/5的厚度是不连通的,只有下部1/5的厚度是连通的;辫状河砂体内部呈冲刷充填结构,单个河道单元厚度为2～5m,由于河道快速频繁的摆动使多个成因的砂体在垂向及侧向上相互对接,形成了广泛连通的厚砂体。通过对研究区开发动态特征的分析认为,辫状河砂体的采油速度和采收率等开发指标均优于曲流河。

During the Neogene period,fluvial sedimentary system was well developed in Bohai area. Different types of fluvial sand bodies have various interconnectivity architecture and development characteristics. Based on the core observation and data of infill well patterns,the sandbody interconnectivity architectures of high-sinuosity meandering river and sandy braided river were deeply studied respectively by means of analytical hierarchy process,and the connectivity models of the two types of sand bodies were established subsequently in Nm formation,Neogene,Qinhuangdao 32-6Oilfield,Bohai area. Generally there are 30 to 200 lateral accretion sand bodies in a point bar. The thickness of a single lateral accretion is 1 to 3m. The upper 4/5 thicknesses of the sand bodies is not connected,while the lower 1/5 thickness is connected. The scour-infill structure is present in the braided-river sand bodies,and the thickness of a single river unit is 2 to 5 m. As the rapid and frequent swing of the river,the sand body units with multi-origin connect with each other in the vertical and lateral. Therefore a wide range of connectivity of thick sand body is formed. Through the analysis of behavior characteristics,development indexes of oil production rate,recovery ratio and so on of the braided river sand bodies are superior to that of the meandering river sand bodies.