Thermo-kinetic analysis and microstructural characterization of fractured-carbonate rock exposed to high temperature

Abstract

A significant amount of the world oil reserves is held in naturally fractured carbonate reservoirs which can undergo temperature-induced changes in structural and physicochemical properties while applying thermal stimulation methods. This study reports thermo-kinetic and microstructural analyses of a fractured-carbonate rock from a Mexican reservoir exposed to high temperatures using thermogravimetry and X-ray micro-computed tomography. Activation energies and reaction mechanism kinetics involved in the thermal degradation of the rock sample were determined through iso-conversional and model-fitting methods. X-ray diffraction revealed the expected mineralogy of the rock sample: dolomite (96.5%) and quartz (3.5%). Results indicated that rock thermal-decomposition follows a first-order reaction kinetics with an average activation energy of 195.910 kJ/mol. Noteworthy microstructural changes were detected on the analyzed fractured-carbonate rock exposed to heat-treatment which resulted in percent increases of 7.47, 4.37 and 25.39% in total, effective and isolated porosity, respectively. Results presented in this work can be relevant for the exploitation through thermal stimulation methods of naturally fractured carbonate reservoirs.