Solid state C NMR studies of selected oil shales from Queensland, Australia

Solid state ¹³C NMR techniques of cross polarization with magic-angle spinning, and interrupted decoupling have been employed to examine the nature of the organic matter in eight kerogen concentrates representing five Tertiary deposits in Queensland, Australia. The NMR results show that five of the kerogens have high proportions of aliphatic carbon in their organic matter and correspond to Type I–II algal kerogens. Three of the kerogens, derived from carbonaceous shales, have a high proportion of aromatic carbon in their organic matter and correspond to Type III kerogens. The fractions of aliphatic carbon in all the kerogens, regardless of type, are shown to correlate with the conversion characteristics of the corresponding raw shales during Fischer assay. Interrupted decoupling NMR results show the presence of more oxygen-substituted carbon in the carbonaceous shales, which may account for the greater CO₂ evolution and phenolic materials found in the pyrolysis products of the carbonaceous shales.     

Cross polarization magic-angle spinning 13C NMR spectra of oil shales

Cross plarization magic-angle spinning ¹³C NMR spectra have been obtained on oil shales representing a variety of geologic ages, origins, depositional environments, and source locations. The spectra show variations in the aliphatic and aromatic carbon distributions of the oil shales and reveal correlations between aliphatic carbon contents and potential shale oil yields. Hints of additional fine structure are present in the spectra of some samples, and examples are given of the spectral resolution that may be obtainable on other solid samples of geochemical interest.     

An NMR survey of United States oil shales

Solid state nuclear magnetic resonance techniques were used to measure the fraction of aliphatic carbon in oil shales from United States deposits, ranging in age from Ordovician to Tertiary. The aliphatic carbon fraction was shown to correlate with the fraction of organic matter converted to oil during Fischer assay. The fraction of organic matter convertible to oil is a primary factor in evaluating the oil potential of an oil shale resource. Nuclear magnetic resonance determines this in a nondestructive, easily interpreted bulk analysis of the whole rock.     

13C NMR measurements of the genetic potentials of oil shales

Cross polarization, magic-angle spinning ¹³C NMR measurements have been made on raw oil shales that represent a variety of geologic ages, origins, depositional environments and source locations. A high degree of correlation was established between the fraction of aliphatic carbon measured by ¹³C NMR, and the genetic potential, calculated from Fischer assay data. The correlation is independent of the type of kerogen in the raw shale, and its degree of evolution. A short discussion on the validity of various correlations between physical/chemical properties of oil shales and Fischer assay oil yields is given.