Fine Reservoir Description Of Chang 6₁ Reservoir In S130 Area Of Ordos Basin

The study area is located in the northeastern part of Wangyao District,Ansai Oilfield,and its tectonic position is on the gentle slope of the north of Shanxi Province.The main oil-bearing strata are the Triassic Yanchang Formation,which belongs to the low-porosity,low-permeability tight sandstone reservoir.Since it was put into production,after many years of waterflooding development,we have obtained rich geological understanding and research results.With the deepening of the development,many problems exposed have restricted the effective development and utilization of reservoirs,mainly because of the large vertical changes in the reservoir and the strong heterogeneity of the reservoir.Therefore,it is imperative to develop detialed reservoir description research in this reservoir.This paper is guided by theories of sedimentology,petroleum geology,logging geology,reservoir geology,development geology,and reservoir description.It uses fine stratigraphic division and comparison,fine sedimentary microfacies research,the construction of the reservoir 3D geological models and other techniques and methods to carry out fine reservoir description studies on Chang 6₁reservoir in the S130 area of the Ordos Basin.Using the core data and log data,the stratigraphic division and contrast analysis of the target strata in the study area are divided and compared.The main reservoir of the study area is divided into 4 small layers,and the reasonable contrast relationship and the small layer reservoir frame are established in the area of the sand layer and the small layer in the area.On the basis of stratigraphic division and comparison,combined with the sedimentary background of the study area,core,logging data and comprehensive sedimentary facies identification marks,the delta front subfacies of the deltaic facies are determined in the study area.On this basis of three kinds of sedimentary microfacies of the subwater distributary main channel,the flanking of the river channel and the inter distributary Bay are further identified.The distribution characteristics of sedimentary microfacies in profile and plane are summarized.In order to meet the needs of the development and geological understanding in the middle and later oil fields,the single sand body of the main reservoir in the study area was carefully identified and divided.Based on the fine division of reservoirs and the systematic study of the characteristics of sedimentary microfacies,the characteristics of spatial distribution of single sand bodies in the reservoir are analyzed.The reservoir characteristics and heterogeneity are studied by microscopic observation,laboratory analysis and logging data.It is found that the reservoir heterogeneity in the target layer of the study area is strong.On the basis of the above geological knowledge,the three-dimensional geological modeling technology of reservoir is used to establish the fine reservoir geological model based on single sand body,and the layer model,structure model and reservoir property model of the target layer are mainly established,which provides the basis for the next step to predict the residual oil distribution and improve the development effect.