Resolving the Nanoscale Chemical Composition of Source Rock using Hyperspectral Photo-Induced Force Microscopy
Source rock or shale is a conglomeration of inorganic minerals – e.g, silicates and carbonates – interspersed with organic matter. Distinguishing the organic and inorganic phases may explain how nanoscale properties influence the properties of bulk rock. While topographic information (a) offers little compositional information, the hyperspectral image (b, hyPIR) provides an IR spectrum at each pixel. A linear display of 10 spectra (c) selected from the hyPIR image distinguishes inorganic rich (d, 1100 cm-1) from organic-rich (e, 1265 cm-1) pixels. The resolution of this method even allows distinction between aromatic (820-870 cm-1) and aliphatic-rich (1265 cm-1) components, a key indicator of the sample’s thermal maturity.
A nanoscale understanding of the rock in unconventional reservoirs has significant implications in determining its hydrocarbon potential and provides new insights for processing.
The results of hyperspectral PiFM studies on shale clearly and powerfully demonstrate the technique’s ability to distinguish between inorganic and organic components in geologic mixtures. The differentiation between materials even extends to subclassifications of organics: aliphatic vs. aromatic.