Reservoir Architecture Analysis Of The Lower Es2 Member In South Wen79

The study area South Wen79 block is located in the south extension part of the Wennan oilfield Dongpu Sunken.After 20 years of extraction and adjustment,the petroleum reservoir is now containing high percentage of water,facing the serious challenge of exploit value and benefit,which has a vital influence on the sustainable development of the oilfield.The reservoir of South Wen79 have many suites of oil-water system,oil and water relationship is complicated.The study of reservoir description draws the conclusion that the pattern of well which control the major petroleum layer have a certain number of uncontrolled sand bodies which indicate that there is still considerable amount of remaining oil and wild spreading sand bodies.Thus,we consider the oilfield has high potential of adjustment and exploitation.To figure out the layout of the remaining oil,one must first make description of the reserving layer's structure which can influence the separation of the fluid,have a knowledge of oilfield's structural geology and have a correct view of the layout property of the micro sedimentary facies,the special settlement of the sand bodies and the reserving space type and connection of the oilfield.Therefore,building on the previous study of the sedimentary faces,this thesis focused on study the reservoir's micro sediment faces,reshape the geological development process and analysis the inner structural of sand bodies of the studied area.The study object is the sub-part of the lower South Wen79 sand.Multi level and systematic comprehensive analysis has been done in the studied area with the cohesive data from well logging,core and many more and the combination of sedimentary,lithology,sequence stratigraphy,well logging,petroleum geology,reservoir geology and related studies serve as the guidance of the study.Through comprehensive study of the area's geology and sedimentary background and observation to the core well logging data,with the combined knowledge of lithology,sediment structural,paleobiology and well face sigh,one can determine the sediment system of the sub-part of the lower South Wen79 sand,identify the structural and feature type of the major micro sedimentary faces and make further conclusion of the structure layout of the sand bodies and the sedimentary method of the reservoir.The key of the study is to anatomise the structure of the sand bodies,see the main factor of how the fluid flow.With the direction of the thought above,several conclusions have been determined:1.First,the study requires the thorough understanding of the area's stratigraphy,structure and reservoir feature.The main reservoir type developed in the area is the structural layer type which is controlled by the lithology of the area,the main productive layer has complex oil-water relationship.In the oil-containing layers' systems of sub-part of the lower South Wen79 sand,the major study area is the sub-part of the lower 2 sand group and 5 sand group which is the main productive layer.The fault has a significant effect on the wen 79 duan block.To the east of the South Wen79 area that has been studied,the Xulou fault has been developed.The west of the area is the wen 43-6 fault.The core of the sediment area is not influenced by the fault,the whole landscape appears to be flat.2.According to the data of core observation,granularity analysis,logging curve combined with the regional sedimentary background,we believe that the study area: the 79 Nansha 2 sub section belongs to the shallow water deltaic depositional system,shallow delta front subfacies.Five kinds of distributary channel microfacies: the underwater distributary channel,underwater distributary channel,delta front sheet sand and water have developed.Estuary dam is not developed.The lithology is relatively single,mainly mudstone,sandstone,siltstone.Sandstone is mainly composed of siltstone and fine grain sandstone with a high degree of structural maturity.Many cross beddings,erosion structures,deformation structures,biological traces etc.have been developed.The distribution characteristics of sedimentary microfacies show that the width of the sand body's channel is narrow,the thickness is thin,and the overall continuity is poor.Front edge sheet sandstone has a good continuity.3.Under the constraint of reservoir layer,we make description of the sand body in different time units of the main sand group in the study area.Influenced by the main subject source of the northwest and the north,the direction of the sand body extends from northwest to southeast.The formation of the same composite water diversion system of the distributary channel sand body plane shape for the dendritic River bifurcation increases with increasing distance of the stretching frequency.Single distributary channel sandstone is mainly banded and lay out to the lake center distribution,sand sheet is contiguous distributed in the anterior and lateral margin of river sand.4.Based on fine sedimentary microfacies and distribution of sand body,we analyzed the internal structure of the reservoir sand bodies and identified five kinds of distribution of sand body styles,including low sinuosity meander shaped or bifurcate(herringbone),finger shaped,kidney shaped sheet.Seven kinds of sand body section overlay style has been identified,they can be divided into connected type and isolated type.The connected type include cut stacked,multi-layer cut stacked,single layer cut stacked,single line cut stacked,ploy line cut stacked.Isolated sand body can be connected to form isolated river through sand sheet,eventually forming this type of sheet sand.Sheet sand alone can form stable interbedded sand sheet.Then we analyze the evolution of reservoir sand body development.The main sand body is the underwater distributary channel sandstone and it is carrying out by foreset structure.Reservoir model of the studied area is distributary channel shallow water delta depositional mode with the character of low angle bifurcation,low bend channel and width decreasing with bifurcation.