Study On The Genesis And Distribution Of Effective Sandbody In Lower He8 Member In Block X Of Sulige Gas Field

Sulige Gas Field is the largest tight gas field in China,with the characteristics of low porosity,low permeability and low abundance.The study area is located in the middle of the gas field,the main gas-producing layer is the He8 member of Lower Shihezi Formation and Shanxi Formation.Due to the tight reservoir,the identification of effective sandbodies in the study area is difficult,and the distribution law of effective sandbodies is not clear,which affects the next exploration and development of the gas field.In this paper,the lower He8 member in X area of Sulige gas field is taken as the research horizon.The lithofacies and logging facies of the lower He8 membei are analyzed by core,logging and logging data.The types of sedimentary microfacies in the study area are divided,and the single well facies and well-connected facies are establ-ished.The plane distribution characteristics of sedimentary microfacies in the lower 1 and lower 2 of He8 member are clarified,and the distribution characteristics of sandbody in the study area are analyzed.According to the definition of the physical characteristics of effective sandbody in the study area,the physical characteristics of the effecti-ve sandbody in the lower He8 member are statistically analyzed,and the causes are analyzed.Finally,the distribution law of effective sandbody in the lower He8 member is predicted and analyzed by geostatistical inversion method.The results show that the lower He8 member in the study area is braided river sediment,which develops three sedimentary microfacies: braided bar,channel retention and flood plain.The braided bar is distributed in the whole area,and most of them are composite braided bar.The sandbody is distributed in the whole area,and the thickness is large.The main sand belt is characterized by north-south distribution,but the effective sandbody is locally developed.The effective sandbody is characterized by multi-phase superposition,showing the characteristics of north-south strip distribution.The distribution range and thickness of effective sandbody in the lower 2 member of He8 are larger than those in the lower 1 member of He8,which should be the main development target.The formation and distribution of effective sandbody are largely controlled by rock components and sedimentation.The higher the quartz content in the rock components,the better the physical properties,which is conducive to the formation of effective sand bodies.At the same time,sedimentation makes effective sandbody mainly develop in the heart beach microfacies,the correlation between porosity and permeability of effective sandbody in the target layer of the study area is not obvious.The reason is that diagenesis has a great influence on the physical properties of effective sandbody.The dissolution and chlorite cementation action play an positive role in the formation of effective sandbody.Compaction,kaolinite and illite cementation have certain destructive effect on effective sandbody.Through research,it is helpful to understand the characteristics and distribution of effective sandbody in the lower He8 member in the study area,improve the development efficiency of the study area,and also provide reference for the prediction of effective sandbody in the study area and adjacent blocks.