Study On Reservoir Heterogeneity Of The P?2 Sand Group In The Middle West-2 Area Of South Block In Lamadian Oilfield

Lamadian Oilfield is located in the north of Daqing Placanticline and belongs to fluvial-delta sedimentary system.After years of development,second sand group of Putaohua I reservoir group(PI2 sand group)in the west of middle-south block 2 of Lamadian Oilfield has entred ultra-high water cut stage,and some problems have arisen,such as serious ineffective injection-production cycle,poor water-flooding development effect,difficulty in tapping oil potential through water control.In order to further improve the oilfield exploration development effect,improve overall recovery factor of the area,it is necessary to meticulous depiction of the PI2 sand group reservoir unit in the study area,deeply analyze and understand the characteristics of sedimentary microfacies and reservoir heterogeneity under the scale of single sand layer.In this paper,according to the characteristics of sedimentary cycles,the P?2₁ and P?2₂thin layers in the PI2 sand group are subdivided into two single sand layer(P?2₁¹,P?2₁²,P?2₂¹,P?2₂²),and the P?2₃ sand group is subdivided into three single sand layer(P?2₃¹,P?2₃²,P?2₃³),a total of7 single sand layer.Then,the sedimentary facies are studied,the distribution law of sandbody plane and the distributing feature of sedimentary facies belt are summarized.The macro-heterogeneity characteristics of reservoir is studied from three aspects:in-layer,inter-layer and plane.Finally,synthesized each factors affecting of the reservoir heterogeneity,Analytic Hierarchy Process(AHP)is used to calculate the heterogeneous synthetic index to quantitatively characterize the macroscopic heterogeneity of the reservoir,quantitative characterization the macro-heterogeneity characteristics of reservoir in study area.The results show that:firstly,influenced by the provenance in the Northeast direction,the PI2 sand group in the west of middle-south block 2 of Lamadian Oilfield belongs to braided river facies.River beds and floods are mainly developed in the study area.Riverbed and river flood subfacies are mainly developed in study area,which can be further divided into channel,diara,floodplain,flood plain micro-facies types.The channel and diara are the main micro-facies types in the study area.Secondly,PI2 sand group mainly develops positive rhythm and homogeneous rhythm;The types of interbed are mainly physical interbed and argillaceous interbed;the permeability within the layer is quite different,and the heterogeneity within the layer is strong overall.Thirdly,the P?2₃thin layer is the best developed sandbody in the PI2sand group;the physical properties of the three thin layers are quite different,and the heterogeneity of inter-layer physical properties is strong;the development of the whole restraining interlayer between single sand is stable.Fourthly,the sandbody distribution in the PI2 sand group is controlled by the sedimentary facies.The thickness of the sandbody in the diara micro-facies is the largest,and the thickness of the channel microfacies sandbody is relatively small.The plane distribution of reservoir physical parameters has a certain similarity,there are many high-value points in the diara micro-facies,and low-value points are mostly present in the channel micro-facies;the permeability coefficient of variation shows that the reservoir plane heterogeneity is strong.Fifthly,integrating the various reservoir factors affecting heterogeneity,using the analytic hierarchy process to calculate the heterogeneous synthetic index,and classifying the reservoir heterogeneity into four levels according to the numerical size,it is concluded that the PI2 sand group in the west of middle-south block 2 of Lamadian Oilfield reservoir heterogeneity is mainly middle to stronger.