TGA and elemental analysis of type II kerogen from the Bakken supported by HRTEM

Abstract

In this study, non-isothermal thermogravimetric analysis was conducted on three samples taken from the Bakken Formation at one heating rate (10 °C/min). Based on the TGA thermograms, various intervals of weight loss were identified. The differences in weight loss, peak positions, and shapes of the samples’ thermograms were attributed to the variations in the composition (quantities of silicates and clay minerals), TOC content, and thermal maturity of the kerogen. Moreover, it was observed that the sample with the highest thermal maturity had the highest number of aromatic rings in its structure. XRD analysis demonstrated that the sample with the lowest silicate concentration and the highest clay mineral content lost the most weight during TGA analysis. Furthermore, CHNS elemental analysis indicated that samples with higher thermal maturity levels have higher amounts of C and H elements and lower content of N and S heteroatoms. Ultimately, our results were corroborated by HRTEM (High Resolution Transmission Electron Microscopy) analysis of p-kerogens, thus confirming the abundance of aromatic rings in the samples and delineating the relationship between aromaticity and thermal maturity.