Micro-Spectroscopic Characterization of Organic Matter in Geological Systems

Organic matter in sedimentary rocks controls hydrocarbon generation, carbon sequestration and palaeoenvironmental reconstructions. Micro-spectroscopic approaches—including micro-Fourier transform infrared (micro-FTIR) spectroscopy, atomic force microscopy-infrared spectroscopy (AFM-IR), synchrotron infrared nano-spectroscopy and Raman spectromicroscopy—enable direct, in situ measurement of chemical composition, functional group distribution and mechanical properties at micrometre to nanometre scales. These techniques reveal heterogeneity in molecular structures of kerogen and organic macerals, elucidate mineral–organic interactions in pore networks and track thermal maturation pathways during burial. Correlative multi-modal workflows combine sequential or simultaneous spectral imaging with electron microscopy, mass spectrometry imaging and X-ray spectroscopy to construct three-dimensional maps of organic constituents and their elemental or isotopic signatures. Such high-resolution chemical maps underpin refined models of hydrocarbon generation, storage and flow in shale reservoirs, improve assessments of organic carbon retention in sedimentary environments and support exploration of unconventional resources. Beyond energy applications, micro-spectroscopy informs reconstruction of palaeoclimatic conditions via organic biomarkers, guides CO₂ sequestration strategies in subsurface formations and enhances understanding of organic material preservation in geological archives.

Research from Nature Portfolio

Recent studies have applied AFM-IR to document nanoscale chemical and mechanical heterogeneity of organic matter in shale. One foundational investigation combined AFM-IR with optical microscopy to characterise individual macerals within artificially matured shales, revealing how chemical composition evolves during petroleum generation at spatial resolutions unattainable by conventional infrared imaging. Another work introduced synchrotron infrared nano-spectroscopy coupled with machine learning to integrate chemical maps across micrometre and nanometre scales. This approach generated deconvoluted distribution models of kerogen and mineral phases, unravelling co-localisation patterns critical to gas sorption and transport. Together, these advances demonstrate the power of high-throughput, cross-scale spectroscopic imaging for detailed geochemical characterisation of organic-rich formations.

Micro-Spectroscopic Characterization of Organic Matter in Geological Systems publication trend

The graph below shows the total number of articles in micro-spectroscopic characterization of organic matter in geological systems across all publications each year (not limited to Nature Index journals).

Technical terms

Atomic force microscopy-infrared spectroscopy (AFM-IR): A technique that couples AFM with infrared spectroscopy to measure local chemical composition and mechanical properties at nanometre resolution.

Micro-FTIR spectroscopy: Fourier transform infrared spectroscopy performed with micrometre-scale spatial resolution for mapping functional groups in situ.

Synchrotron infrared nano-spectroscopy: High-brilliance infrared technique using synchrotron radiation and nanoscale probes to obtain chemical images with nanometre resolution.

Kerogen: Insoluble organic matter in sedimentary rocks that generates hydrocarbons upon thermal maturation.

Chemometric modelling: Application of statistical and multivariate analysis to spectroscopic data for quantitative prediction of geochemical parameters.

References

1. Nanoscale geochemical and geomechanical characterization of organic matter in shale. Nature Communications (2017).
2. Cross-Scale Molecular Analysis of Chemical Heterogeneity in Shale Rocks. Scientific Reports (2018).
3. A review of spatially resolved techniques and applications of organic petrography in shale petroleum systems. International Journal of Coal Geology (2021).
4. Infrared spectroscopy and chemometric modelling of organic carbon measured by Rock-Eval pyrolysis of UK shale rock. Geological Society London Special Publications (2023).
5. Mineral Heterogeneity Characterization of the Lacustrine Yanchang Shales, Ordos Basin Using Micro‐Fourier Transform Infrared Spectroscopy (Micro‐FTIR) Technique. Geofluids (2021).