Study On Reef-shoal Architecture And Reservoir Characteristic Evaluation In S Gas Field Of Central Asia

Architecture research is a fine description technology of petroleum reservoirs by describing the shape,scale,distribution space and superposition relationship of configuration units.It plays an important role in petroleum reservoir research and efficient development.At present,the architecture research is mainly focused on clastic rock,and the related technologies and methods are relatively mature.As for architecture of the carbonate rock,due to the influence of various diagenesis from the beginning of deposition to burial,the controlled factors of reservoir are complex,and the reservoir characteristics are more complex.Generally speaking,there is still a lack of systematic research on the carbonate rock reservoir Architecture.The layer XVp and XVm of the Callovian-Oxfordian carbonate formation of Middle-Upper Jurassic in S gas field where located in the right bank of Amu Darya River are taken as the target.Previous studies have confirmed that the reservoir of the study is mainly controlled by reef-shoal facies,and the later diagenetic transformation has little influence,which meets the requirements of facies controlled carbonate reservoir architecture.Therefore,this thesis takes the reef-shoal reservoir as object,and subdivides the XVp and XVm through the identification of marker layer and sequence stratigraphic correlation.Evaluate the characteristics of various types of microfacies of the gas field,establish the identification template of carbonate logging facies,describe the distribution of reef and shoal,and show the sedimentary evolution process of each secondary layer of reef and shoal.Based on the logging characteristics of core,thin section and reef-shoal facies,the interface between reef and shoal is determined.The boundary of reef and shoal is determined by the leveling method of base level layer,according to the difference characteristics of lithology,logging shape and microfacies,and combined with seismic data.Based on the results of interface and boundary identification,the scale of shoal and reef is described by using the dense well pattern of gas field,and the scale model of shoal and reef in the study area is established.Through the superposition relationship of shoal and reef in space,the architecture types of shoal and reef are summarized respectively.Through the evaluation of reservoir characteristics of reef-shoal with different architectures,the reservoir characteristics of various reef-shoal are summarized.Taking the plane distribution of each secondary layer reef and shoal and the interpretation results of logging reef and shoal as spatial constraints,the geological model is established,and the gas-bearing enrichment areas of reef and shoal with different architectures are determined according to the gas-bearing distribution corresponding to the geological model of reef and shoal.Through the above research,the following achievements have been achieved:(1)Through the study on the secondary layer subdivision of XVm and XVp and the characteristics of microfacies,the distribution characteristics of reef(XVm)and shoal(XVp)in each secondar layer are clarified.Through the method of marker layer correlation and sequence stratigraphic division,the XVm is subdivided into four sets of secondar layers,namely XVm1,XVm2,XVm3 and XVm4,and the XVp is subdivided into three sets of secondary layers,namely XVp1,XVp2 and XVp3.Based on the previous understanding of regional sedimentary characteristics,through the evaluation of microfacies and logging facies of the target,it is clear that the dominant microfacies of XVm is platform margin reef,and the dominant microfacies of XVp in the gas field is platform margin shoal.The logging interpretation results of reef-shoal facies are corresponding to the well points of each secondary layer,depicting the plane distribution of shoal and reef,and showing the sedimentary evolution process of reef and shoal.It is concluded that four sets of secondary layers of XVm show the evolutionary characteristics of gradually increasing reef development scale from bottom to top.XVm1 and XVm2 are the early stage of reef development,XVm3 is the middle stage of reef development,and XVm4 is the peak stage of reef development.The the shoal of XVp is distributed in flakes in each secondary layer,in which XVp1,XVp2 and XVp3 correspond to the early,middle and late stage of shoal development respectively.(2)Carry out quantitative evaluation of shoal and reef and division of architecture types.According to the idea of architecture classification in reverse order,the classification system of reef-shoal architecture of the target in the study area is established from macro to micro.Through the determination of lithologic interface and dominant microfacies logging characteristics of reef and shoal,the marks of reef and shoal interface are clarified,and the boundary division marks of reef and shoal are summarized according to "the differences of lithology,logging shape and microfacies" combined with seismic facies data.Based on the recognition results of reef-shoal interface and boundary,based on the gas field well pattern,the scale of shoal and reef is described through the idea of "point-line-surface",and the scale models of shoal and reef are established respectively.According to the relationship between reef and shoal in space,three types of reef architectures are summarized:vertical superimposed reef,lateral superimposed reef and independent reef,and three types of shoal architectures are summarized: vertical superimposed shoal,lateral superimposed shoal and independent shoal.Through the description of the spatial architecture of reef and shoal in each secondary layer,it is clear that independent reefs mostly appear in the early stage of reef development(XVm1 and XVm2).Lateral superimposed and vertical superimposed reefs mostly appear in the middle and peak stages of reef development(XVm3 and XVm4),andindependent and lateral superimposed shoal mostly appear in the early stage(XVp1)and late stage(XVp3)of shoal development,and vertical superimposed shoal mostly appear in the middle stage(XVp2)of shoal development.(3)Evaluate the petrological characteristics,reservoir space types,pore throat structure and physical properties of reef-shoal reservoirs with different architectures.It is clear that there is no obvious difference in the classification of reservoir rock types and reservoir space types of reef and shoal with different architecture types.From the perspective of sedimentary evolution and reef-shoal scale,it is summarized that the shoal and reef form superimposed shoal and superimposed reef with large scale and thickness in the rapid growth aggradation stage.At this stage,the reef-shoal has high development maturity,and the corresponding reservoir pore throat structure is mainly coarse throat with medium to large pores,with well reservoir porosity and permeability.In the early stage of shoal and reef development,independent shoal and independent reef with small scale and thickness are mostly formed.In the early stage,reef and shoal are immature.The reservoir pore throat structure of these two reef and shoal architectures is mainly small pore and fine throat,and the pore and permeability properties of the reservoir are poor.According to the study on the heterogeneity variation coefficient of reef beach reservoirs with different configurations,except for the medium heterogeneity in the independent beach reservoir,the reef beach reservoirs with other configurations in the study area are weakly heterogeneous.(4)Taking the reef-shoal interpretation results of logging as hard data and the plane distribution of reef-shoal architecture as spatial constraints,the facies model of reef-shoal are established.Based on the logging interpretation results of porosity,permeability and saturation,and constrained by the facies model of reef-shoal,the attribute model of reef-shoal is established by using the sequential Gaussian random modeling method.The attribute model shows that the porosity and permeability properties of vertical superimposed and lateral superimposed reefs have composite anti rhythm characteristics.The porosity and permeability properties of the front zone of independent reefs are better than that of the back zone of reefs under the influence of waves.The physical properties of porosity and permeability of vertical superimposed shoal show the characteristics of "the interior is good and the exterior is poor".The physical properties of independent shoal and lateral superimposed shoal are generally poor.According to the distribution characteristics of model reserves corresponding to reef-shoal with different architectures,it is clear that the large-scale overlapping area of reef and shoal is the gas-bearing enrichment area of gas reservoir.Through the comparison of test results of typical wells,it is confirmed that the research on reef shoal reservoir architecture is highly reliable.Through the research on reef-shoal architecture and the evaluation of reservoir characteristics of reef-shoal with different architectures,it provides technical reference for the fine characterization of reef-shoal in the right bank of Amu Darya River and the efficient development of similar gas reservoirs.