Studies of Polish Paleozoic shale rocks using FTIR and TG/DSC methods

Abstract The presented investigation is focused on fine-grained Palaeozoic (Silurian and Carboniferous) rocks collected from several wellbores in Poland. The implemented methods are: diffuse reflectance infrared fourier transform spectroscopy (DRIFT) thermal methods (TG/DSC), as well as XRD and Rock-Eval pyrolysis. These methods made it possible to determine the composition of the samples tested, including the presence of minerals and organic matter. The DRIFT technique of FTIR analysis was implemented, because in case of DRIFT technique the high frequency bands are usually more informative with respect to detection of aromatic and aliphatic bands in the examined rocks, compared to other techniques of IR (e.g. ATR). The occurrence of aromatic groups in the samples is the evidence of higher kerogen maturity. Thermal methods (TG/DSC) made it possible to trace the reactions during heating the samples in an oxidizing and inert atmosphere. The pyrolysis peaks in DSC curves indicate kerogen of type II, which agrees with a classification based on Rock-Eval measurement. Basing on the DTG curves the maximum temperature of the pyrolysis peak could be determined, and in a consequence – the thermal maturity of the organic matter in the sample. The enthalpy of organic matter in examined samples, calculated from DSC curves correlates very well with TOC value (Rock Eval), what demonstrates that thermal analysis can be successfully used to determine the content of organic matter in fine grained rocks, such as gas-shales or similar ones.