The study investigates the structural and surface changes occurring in carbonate drilling sludge (CDS) of oil-based origin under high-temperature pyrolysis. The main focus is placed on the transformation of the organo-mineral system using IR spectroscopy, as well as on the changes in textural characteristics analyzed by adsorption–pore methods (BET and BJH). It has been established that pyrolysis ensures the complete removal of the organic fraction of the sludge, which is confi rmed by the disappearance of characteristic aliphatic hydrocarbon bands in the IR-spectra.