Potential Raman parameters to assess the thermal evolution of kerogens from different pyrolysis experiments

Potential Raman spectral parameters of kerogens are discussed in this work to evaluate the thermal maturity of organic matter. Four series of simulation experiments were carried out, including the semi-open system, closed golden tube system and two sets of closed glass tube system. Samples were treated for 72 h within the temperatures range 280–560 °C. The results showed that the Raman parameters, such as the shift of the spectral peaks G (∼1600 cm−1) and D (∼1350 cm−1), D/G ratios (based on area, height or width) and the inter-peak interval between peaks G and D, varied regularly with increased thermal maturity. However, some results from the closed glass tube systems were different from the other two pyrolysis systems, which can be attributed to the different cracking characteristics of kerogen macromolecules under different conditions. This observation is quite revealing and we therefore suggest that different simulation models should be employed to study the geological samples from specific geological backgrounds, and multiple parameters should be examined for optimal constraints.