Architecture Anatomy Of Meandering River Reservoir Of E₂s₁^4-5 In Zhenwu Oilfield

Zhenwu oilfield is one of the typical oilfields in the North Jiangsu basin with large oil-bearing area and high oil and gas enrichment.After more than 40 years of development,it has entered a high water cut period,but the recovery rate is low at36.6%,and there is still a large amount of remaining oil that has not been extracted.In view of the structural characteristics of the mud-coated sand in the E₂s₁^4-5sand group of Zhenwu Oilfield and the distribution characteristics of the remaining oil overall dispersion and local concentration,the sedimentary facies in the study area were analyzed in detail,and the meandering river reservoir architecture model in the study area was clarified.The fine anatomy of the reservoir architecture,especially the characterization of the lateral accretion body inside the point bar,summarizes the distribution characteristics of the remaining oil under the control of the reservoir architecture,and provides a basis for the exploitation of remaining oil resources.Based on the core,logging,seismic and other data,this paper uses sedimentary cycle correlation,three-dimensional seismic constraint and sedimentary model facies controlled trend tracking and other comparison methods to carry out stratigraphic division and fine correlation of small layers.Based on the study of sedimentary facies of E₂s₁^4-5sand group,the architecture model of meandering river reservoir suitable for E₂s₁^4-5sand group is summarized.Under the guidance of the model,the reservoir architecture is characterized and depicted in detail.On this basis,combined with dynamic data,the distribution characteristics of remaining oil under the control of reservoir architecture are summarized.Research shows that:（1）The sedimentary cycle in the study area is a long-term cycle,including 5medium-term cycles,which can be further divided into 14 short-term cycles.（2）The E₂s₁^4-5sand layer in the study area is meandering river deposition,and the sedimentary characteristics are"mud-coated sand"structure.The main sedimentary subfacies are riverbed subfacies,embankment subfacies and flood subfacies.The main microfacies are river channel,point bar,crevasse splay,natural levee,floodplain,flood swamp and abandoned channel.The main configuration elements include river channel,point bar,floodplain and flood swamp,and crevasse splay is developed locally.The river is a high curved river,and the point bar is mostly a single point bar.（3）The E₂s₁^4-5sand layers identified 3～6 level configuration interface and sand body,which can be divided into 14 single layers from bottom to top.The 6th interface is the interface between E₂s₁⁵sand group and E₂s₁⁶sand group.The 5th interface is the interface between 14 small layers;the 4th interface is the interface between various genetic sand bodies;the third-level interface is mainly the interlayer inside the single sand layer,that is,the muddy interlayer between the lateral deposits inside the point bar.（4）The plane structural style of meandering river in the study area is point dam-river tangent and point dam-point dam tangent.Vertically,due to the mud-coated sand structure,the sand bodies are all composed of muddy sediments,and vertically,the sand bodies are distributed in isolation.（5）The remaining oil resources in the study area are mainly controlled by reservoir architecture,mainly distributed in the edge and top of the single point bar,the edge and top of the composite point bar and the contact parts between different configuration elements.