Lithology Determination From The Micro-seismogram

The location and identification of lithology changes has been effected by use of the Micro-Seismogram Log. Conspicuous phasing patterns caused by the interaction of compressional and shear energy of the acoustical signal have been observed to be associated with particular lithologies. Patterns caused by relatively slow shear energy have been correlated to anhydrite and limestone lithologies while relatively fast shear energy has been correlated to chert and dolomite lithologies. The correlations were made using standard Micro-Seismogram logs recorded in open and cased holes located in the Permian Basin. Examples showing abrupt and gradational lithology changes are presented for limestone-dolomite, limestone-chert, limestone-sand, and dolomite-anhydrite. Use of the phasing patterns in single and dual lithologies to predict matrix transit time is discussed.