Inversion Of Thin Interbed Array Induction Logging Of Sandstone And Mudstone

Sand-mudstone thin interbed is an important oil and gas reservoir,which has a certain degree of distribution in many oil and gas basins in China.With the improvement of oil and gas exploration and development in China,the identification and accurate interpretation of thin interbeds of sandstone and mudstone are becoming more and more important.Array induction logging has high vertical resolution and has great application advantages in identifying thin interbeds of sandstone and mudstone.However,its response is easily distorted by various environmental factors,which cannot effectively reflect the real resistivity information of the reservoir.Therefore,it is necessary to carry out corresponding inversion processing.Different thin interbed models are established,and the forward response of array induction logging is numerically simulated by finite element method.Skin effect correction and borehole correction were carried out on the apparent conductivity of array induction logging subarray,and the target function conforming to the radial detection characteristics of array induction logging tool was designed,so as to realize forward calculation corresponding correctness.The forward response of array induction logging with different thin interbed models is numerically simulated,and the rules are summarized,which lays a foundation for the later inversion work.An intelligent optimization algorithm(differential evolution algorithm)which is widely used in array lateral logging inversion and less used in array induction logging inversion is introduced into array induction logging inversion,and some improvement measures are given.In order to improve the inversion accuracy of sand-shale thin interbeds,the forward responses of different thin interbed models are added as constraints to the improved differential evolution algorithm.By comparing the processing results of the two algorithms in 100 random inversion calculations,it is found that the improved differential evolution algorithm has better performance.In order to verify the applicability of the improved differential evolution algorithm in complex environments,the forward responses of array induction logging with 5 %,10 % and 20 % Gaussian white noise are inversed.The results show that the improved differential evolution algorithm still has good applicability in complex environments.The improved differential evolution algorithm is used to invert the actual array induction logging data,and the inversion algorithm is verified by using the resistivity logging data while drilling and the oil test and sampling data.The results show that the inversion effect is good,and the trend of inversion formation resistivity curve is basically the same as that of resistivity logging while drilling,which is closer to the resistivity curve level with drilling than the array induction logging depth detection curve M2 RX.At the same time,the oil test and sampling data are used to verify the correctness of the array induction logging inversion effect of the actual thin interbed formation and the improved differential evolution algorithm.The oil saturation calculated by inversion formation resistivity is more in line with the actual data than that calculated directly by M2RX.