This study focused on the characterization of heavy and medium grade crude oils in limestone matrix using differential scanning calorimeter (DSC) and thermogravimetry (TG-DTG). DSC and TG-DTG curves produced for two different crude oils + limestone mixtures indicate that the crude oil undergoes two major transitions when subjected to an oxidizing and constant rate environment known as low- and high-temperature oxidation. Kinetic analysis in the low- and high-temperature oxidation regions were performed using two different kinetic methods. Throughout the study. it was observed that the activation energy values of the samples are varied between 2.40-10.62 and 42.3-181.9 kJ/mol in low- and high-temperature oxidation regions respectively. (C) 2011 Elsevier B.V. All rights reserved.