Atomic force microscopy and infrared spectroscopy combine to give close-up look at organic matter in shale

Shale, a sedimentary rock that is a rich source of petroleum, consists of solid organic matter scattered in a mineral framework. Scanning electron microscopy reveals that neighboring organic matter particles often differ greatly in porosity, but such measurements reveal little about their underlying chemical compositions. Andrew E. Pomerantz of Schlumberger-Doll Research Center and coworkers have now used atomic-force-microscopy-based infrared spectroscopy for nanoscale chemical and mechanical characterization of organic matter from the New Albany Shale geological formation (Nat. Commun. 2017, DOI: 10.1038/s41467-017-02254-0). “This approach gives a glimpse into the composition of discrete particles of organic matter that are too small and too close together to be resolved by traditional chemical imaging tools,” Pomerantz says. Using the method, the researchers found that during artificial maturation the composition of some types of organic matter changes dramatically, whereas the composition of others changes very little. Commenting on the work, Benoit Coasne, a physicist at Grenoble Alps University, notes that although solid organic matter in shale remains poorly understood, “being able to characterize at the nanoscale its mechanical and chemical disorder in a combined way is definitely a big step in the right direction.”