Thermochemical investigation of the oil shale from the Early Cretaceous Garau Formation, Lorestan, SW Iran: Preliminary TGA-FTIR results

Abstract

The oil shale is a prodigious immature kerogen-rich resource, which represent an outstanding potential of oil generation through thermochemical processing at ~350-530°C depending on kerogen peculiarities. Kinetic investigation is one of the fundamental approaches for quantifying and evaluation of this process. The main aim of this study is thermal and kinetic investigation on the Garau oil shale (Early Cretaceous) from Lorestan province of Iran using TGA-DTG analysis (Thermogravimetry Analysis; TGA and Differential Thermogravimetry Analysis; DTG) under three constant 5, 10, 15 °C/min heating rate from 20°C up to 900 °C. The FTIR (Fourier transform infrared spectroscopy) analysis was used to evaluate the evolved gases during thermochemical decomposition of the Garau oil shale. The results show the combustion process of the representative sample from the Garau oil shale involves two main peaks of mass loss, which reveal two main reaction regions. The first reaction region is originated from organic matter (bitumen & kerogen) decomposition and the second reaction region is occurred as the result of calcite thermal breaking down. According to the average activation energy calculated for the organic matter decomposition (~183 kJ/mol), the Garau oil shale corresponds to medium-fast reaction rate kerogens, in consistent with IIS-kerogen reaction rate (144-218 KJ/mol).