Carbonates thermal decomposition kinetics and their implications in using Rock-Eval® analysis for carbonates identification and quantification

Abstract

In 2014, Pillot et al. [Identification and quantification of carbonate species using Rock-Eval pyrolysis, Oil Gas Sci. Technol. – Rev. IFP 69, 341–349. https://doi.org/10.2516/ogst/2012036] proposed to use the Rock-Eval® method as a reliable tool to identify and quantify carbonates in solid samples from the CO2 flux emitted by their progressive thermal decomposition during programmed heating under oxidant atmosphere. Nevertheless, several phenomena associated with the thermal decomposition of carbonates were not explained by these authors. This paper attempts to explain these phenomena by adding 5 new carbonate species to the 9 studied by Pillot et al. https://doi.org/10.2516/ogst/2012036 and by developing a kinetic approach to the thermal decomposition of carbonates. It appears that the kinetics of thermal decomposition of most carbonates is not of order 1 but varies according to carbonate species. Consequently, the thermal decomposition temperature varies with both the sample weight and the temperature rate applied. The thermal stability of simple carbonates is explained by the electronegativity of the cations associated with the carbonate anion. Our study provides further insights into the use of Rock-Eval® for the identification and quantification of different carbonate species.