Study On Sedimentary Microfacies Of Fuyu Reservoir And Its Control On The Distribution Of High Quality Reservoir In Rang 58 Area,jilin Oilfield

Under the guidance of high-resolution sequence stratigraphy and comprehensive application of core and well logging data,aiming at the areas with large well spacing and lack of seismic data represented by Jean 58,13 small layers of Fuyu oil layer in Qian'an area are subdivided into 22 sedimentary time units and a single sand body isochronous stratigraphic framework is established with the guidance of marker layer controlling the top and sedimentary model and local reference to layer restriction.In this framework,the types and distribution of sedimentary microfacies are studied in detail in combination with the characteristics of provenance and sedimentary system.A typical river controlled shallow water delta is developed in Fuyu reservoir of Qian'an area.In the early stage,the delta plain is the main deposit,and the distributary channel,natural levee,overflow bank sand and inter distributary microfacies are developed.In the later stage,the delta front deposit is transited,and the underwater distributary channel,river control bar,sheet sand and inter distributary microfacies are developed.Based on the analysis of the distribution characteristics of sedimentary microfacies in different sedimentary time units,this paper puts forward the plane distribution characteristics of "early development is not balanced,middle and late stages tend to be balanced" and the vertical distribution characteristics of "early sedimentary microfacies type is single,large scale,serious superposition,middle stage is small,limited,multiple isolated,late sedimentary microfacies type is rich,small scale,weak shearing degree" ? Based on this,the sedimentary model of Fuyu oil layer in the area of rang 58 is established,which includes the model of "river controlling banded body" in the delta plain area,the model of "nearshore sedimentation" in the delta transitional area,the model of "river controlling plane body" in the inner front area of the Delta,the model of "river controlling sheet sand at the end of underwater distributary channel" and "wave controlling sheet sand" at the top of Fuyu oil layer.On this basis,the internal structure of the composite sand body is mainly analyzed,and it is pointed out that the internal structure of the composite sand body can be divided into three types of vertical superposition,namely,cut superposition type,superposition type and separation type,as well as three types of plane combination,namely,side cutting type,side connection type and separation type.It is proved that the contact relationship of vertical shearing and plane side cutting is the main reason for the formation of composite sand body with wide area and large thickness.Make full use of the geological and oil-bearing characteristics of the study area,establish the classification standard of high-quality reservoir,and divide the high-quality reservoir into four types according to different permeability and porosity,of which class I high-quality reservoir has the best porosity and permeability and class IV the worst.Based on the study of the distribution characteristics of the sand bodies of different types of high-quality reservoirs,it is revealed that the high-quality reservoirs in the study area are mostly distributed in the(underwater)distributary channel microfacies,which are distributed from southwest to northeast;the development of high-quality reservoirs in the delta plain period is better than that in the delta front period.This paper puts forward a high-quality reservoir grading controlling factor model of "superimposed characteristic controlling location,microfacies type controlling location" in tight sandstone of Qian'an area.The sedimentary location of the distributary plain subfacies of the delta is the dominant location for the development of high-quality reservoirs in the region.The vertical and lateral cutting of the river channel is serious,and the reservoir scale is large.The middle and lower part of the internal channel sand body is the main development location of high-quality reservoirs.The high-quality reservoir types are mainly class II and class III,forming a wide belt inlaid with multi-channel sand bodies.The sedimentary location of the delta front subfacies In addition,the vertical and plane cutting capacity of sand body becomes weak,mainly of superposition type and separation type,and the reservoir scale becomes smaller.The internal high-quality reservoirs are mainly concentrated in the middle and lower part of the underwater distributary channel sand body,and the middle and upper part of the river control bar and sheet sand.The high-quality reservoirs are mainly of class II,which are generally shown as thin-layer surface bodies with good quality.By using this model,the prediction accuracy of high quality reservoirs in tight sandstone can be improved,and the production and development of tight oil can be guided.