A Saturation Evaluation Method In Tight Gas Sandstones Based On Diagentic Facies In L Block

The saturation evaluation of tight sandstone reservoir is one of the key parameters of reservoir evaluation,reserve calculation and oil and gas reservoir evaluation.The most commonly used method of saturation calculation is using the logging curve and the data of the rock and electricity experiment,based on the classic Archie model."Non-Archie" phenomena are common in tight sandstone reservoirs with complicated pore structure in L Block,Ordos Basin,China,bringing challenges to the logging evaluation of tight sandstone.Based on the analysis and test data of core casting thin slice,X-ray diffraction,scanning electron microscope,core mercury injection experiment,physical property and rock electricity experiment,the diagenetic facies classification of the studied block is studied at first,on the basis of which,For the first time,the conductivity mechanism and saturation model of different diagenetic facies in dense sandstone reservoirs in the study area are systematically discussed.The study shows that there are mainly 7 diagenesis types in the study area.The classification scheme of three diagenetic facies,which are identified based mainly on diagenesis type,mechanism,and damage to reservoir construction caused by pore types and have been established.The theoretical pore structure models of three diagenetic facies(network model,reticular pore model and dotted line model)and conductive model are established.The electrical parameters of the construction facies are mainly controlled by the pore structure.The saturation model of the construction facies can be explained intuitively from the concept model of pore structure,the pore structure of cemented phase has little change,the saturation exponent n is stabilizing near 2.3,and the saturation model of cemented phase is characterized by the variable parameter Archie model.The clay of the destruction facies leads to the development of matrix intergranular pores and the increase of saturation exponent n.The saturation model of the destruction facies is characterized by the clay conductive model.Finally,the deep autoencoder is used to automatically abstract and express the response characteristics of different diagenetic facies,and the random forest algorithm,which is sensitive to small samples,is used to establish the logging criteria for different diagenetic facies.The saturation model based on diagenetic facies is applied to the saturation logging evaluation of the study block.The reliability of the saturation model proposed in this paper is verified by comparing the log prediction value with the saturation value of the rock sample experimental analysis.It also provides reference for saturation logging evaluation methods in similar research areas.