Study On Logging Evaluation Technology Of Waterflooded Zone Based On Curve Reconstruction Method

This paper takes low permeability reservoir of Chang 2 formation in B region,Jing'an Oilfield and Chang 8 formation in C region Area,Jiyuan Oilfield as main research objects,aiming at the goal of logging evaluation of water-flooded level of low permeability reservoir.Combining with the previous research results,the related research work of water resistivity estimation,SP curve reconstruction,resistivity curve reconstruction by analytical method and machine learning method,and water-flooded layer grade evaluation are carried out.By comparing the changes of log response curves before and after water flooding in low permeability reservoirs,the log response characteristics of spontaneous potential,resistivity,natural gamma ray and sonic time difference curves of water flooded reservoirs and the relationship between natural potential and resistivity curves of different types of water flooded reservoirs(fresh water,produced water reinjection)and the degree of water flooding are clarified.On this basis,the method of combining SP curve reconstruction with resistivity curve reconstruction is proposed to evaluate the watered-out level of low permeability reservoirs.Aiming at the different characteristics of normal resistivity reservoirs in low permeability reservoirs and high resistivity partial parent reservoirs,the analytical resistivity curve reconstruction method based on Archie formula and the machine learning algorithm are established respectively.Analytical resistivity curve reconstruction combined with SP curve reconstruction is suitable for water flooding evaluation of low permeability reservoirs with normal resistivity,and machine learning resistivity curve reconstruction combined with SP curve reconstruction is suitable for water flooding evaluation of medium and high resistivity partial parent reservoirs.Applying this method to the target reservoirs in B region and C region,the evaluation results of reservoir watered-flooded level are in good agreement with the oil testing data and actual production data.