Spectrometric gamma-gamma well logging in exploration of hard coal deposits

The authors have examined the possibilities of a spectrometric gamma-gamma logging method. The method uses the so-called spectrometric parameters calculated as ratios of the intensities of scattered gamma rays measured in two energy windows, the boundaries of each window being selected separately for different purposes: determination of ash in coal, identification of lithology, etc. Quantitative interpretation of continuous readings of these ratios, combined with well diameter data from caliper logging, was done with the help of a calibration equation derived on the basis of multiple correlation analysis of borehole measurements as compared with borecore sample analyses