Organics in oil shale play a significant role in the generation and production of oil gas. Visualizing the content and distribution of organics in the reservoir is the key objective of unconventional resource research. In this study, we demonstrate the application of terahertz (THz) imaging to measure the dielectric properties of oil shale from Huadian and Beipiao with different oil yields. The heterogeneous distributions of organics on the oil shale surface were evaluated by THz amplitude imaging, with the existence of kerogen-rich and kerogen-poor areas identified by different colors. Meanwhile, the average refractive indices of the samples were plotted with the oil yield, revealing a negative correlation between them. Our results prove that THz spectroscopy can provide not only a promising technique to visualize the organic distribution in oil shale but also a convenient means for the quantitative analysis of the organic content in oil shale.

This study demonstrates that oil shale subjected to pyrolysis at 1000 • C strongly absorbs electromagnetic radiation in the terahertz (THz) range. Analyses reveal obvious differences between oil shale samples with and without pyrolysis, as well as between low-middle mature shale and oil shale samples. The electromagnetic absorption effect of oil shale subjected to pyrolysis conditions is demonstrated to be strongly related to its relatively small concentration of pyrite, which progressively yields pyrrhotite and elemental Fe during pyrolysis that facilitates the absorption of THz radiation. Accordingly, oil shale can be used not only as a resource for generating oil, natural gas, and petrochemical products, but the material obtained after processing can also be employed for the absorption of THz radiation as a means of converting incident electromagnetic radiation into heat or other forms of energy, which offers substantial prospects in many engineering and technology applications.INDEX TERMS Oil shale, THz spectroscopy, wave absorbing, pyrite.