Study On Sedimentary Microfacies And Single Sandbodies On Chang 4+5 Member In The Western Jiyuan Oilfield

On the basis of logging data,core data,and analysis data,combing the theories of sequence stratigraphy,logging geology and reservoir geology,the sedimentary microfacies and sandbodies distribution characteristics on Chang 4+5 Member in the Western Jiyuan Oilfield are analyzed,besides the spatial distribution characteristics and width to thickness ratio of single sandbodies in 3 dense well areas are studied.According to the methods of marker layer method,sedimentary cycle and thickness,the Chang 4+5 Member of Western Jiyuan Oilfield is divided into eight sublayers From bottom to top,they are Chang 4+5₂^2-2?Chang 4+5₂^2-1?Chang 4+5₂^1-2?Chang 4+5₂^1-1?Chang 4+5₁^2-2?Chang 4+5₁^2-1?Chang 4+5₁^1-2?Chang 4+5₁^1-1.The source direction of Chang 4+5 Member in the Western Jiyuan Oilfield is mainly the north-east direction,and the parent rocks are mainly metamorphic rocks.The shallow water delta front deposit are mainly developed,which can be further divided into underwater distributary channel,underwater natural levee and and bay sedimentary microfacies.Because of frequent diversion of underwater channel,the sandbodies are mostly distributed.Based on the study of the sedimentary microfacies of eight sublayers on Chang4+5 Member in the Western Jiyuan Oilfield,the sedimentary evolution characteristics are further analyzed.The results show that the sedimentary evolution on Chang 4+5Member is generally lake transgressive and then lake regression,which is characterized that Chang 4+5₂² to Chang 4+5₂¹ is lake transgressive and Chang 4+5₂¹ to Chang 4+5₁¹is lake regression,the lake level of Chang 4+5₂¹ reaches the deepest.Considering the distance from source area,sedimentary facies and dense of well pattern,3 dense well networks are selected to study the identification marks,spatial distribution and evolution characteristics of the single sandbodies.The quantitative prediction model of the width to thickness ratio of the single sandbodies is established to guide the identification of single sandbodies in sparse well networks to realize the qualitatively and quantitatively analysis of single sandbodies.