Thermal evolution of source rocks in sedimentary basin by using electron paramagnetic resonance technique

摘要

Based on the variation of free radicals, thermal evolution of organic matter in source rocks in sedimentary basin can be identified by using electron paramagnetic resonance (EPR) technique. This is based on the changes of free radicals with the evolution of kerogen, which may lead to the changes of EPR spectra. The number of free radicals (spin density, N_g) is related to the temperature during the formation of kerogen free radical; N_g increases with rising temperature of kerogen as a result of cracking paraffin chains in kerogen structure, Morever, free radical may also be formed by expulsion of heteroatoms (O, N, S, etc) from the aromatic sheets, Therefore, EPR technique, based on the variation of spin density, can be used to study the maturity of hydrocarbon source rocks, hence the thermal history of a basin.