Gamma Density Logging Study Based on Sliding Energy Window

To reduce the impact of gap fillings (mud cakes) on measurement results in γ density logging and improve logging accuracy, a sliding energy window method is studied based on the positive correlation between mud cake thickness, density, and peak shift degree; the influence law of mud cake properties on energy spectrum deformation is analyzed; personalized parameter groups and formulas are obtained through fitting sliding energy window counts of known density and mud cake thickness combined with linear interpolation; and forward and inversion verifications are conducted using experimental energy spectrum data from standard wells 4 to 9. The research results show that: ①The influence law of mud cakes is that mud cakes of the same type and thickness cause the same degree of energy spectrum peak shift in different formation calibration wells; heavy mud cakes cause much greater peak shift than light ones; and for the same type of mud cake, the greater the thickness, the greater the shift degree. ②The sliding energy window method can reduce the logging error of the compensation method in most calibration wells and mud cake thicknesses in forward verification, and the calculation error in inversion verification is lower than that of the fixed energy window method. ③In the sliding window averaging method, the effect is better when the sliding window range n=5 and 9. ④This method reduces the average relative error of density logging in standard wells 4 to 9 from 2.08% of the fixed energy window method to 0.67%. It is concluded that the sliding energy window method effectively reduces the impact of mud cakes on γ density logging and significantly improves the accuracy of γ density logging when mud cakes are present.