An electron spin resonance spectrometric investigation of natural,extracted and thermally altered kerogenous materials

Core cuttings from three wells representing a 1000–7000-ft range of depths were examined by ESR spectroscopy. The spectral parameters of some of the series of samples follow trends, as suggested by the ESR kerogen method for paleotemperature estimation, while the spectral parameters of other series of samples do not. Samples extracted with mineral acids exhibit spectra parameters which follow the proposed trends somewhat better, but show large local variations which appear to be due to factors other than paleotemperature. Thermally treated samples show a general increase in free radical concentration, although there are several anomalies. While the ESR-kerogen method of paleotemperature estimation appears to have potential due to the large variations in some of the observed parameters, factors such as mineral acid extraction and sample lithology, among others, need further investigation to refine the technique.