The potential of petroleum source rocks as a dependable energy resource has been recognized and realized by the petroleum industry in the past decade. The production of clean natural gas from these resources and their potential for utilization as carbon storage sites (in adsorbed state) are also aligned with efforts towards mitigating climate change. Optimization of development and production from these resources requires dependable computational models, which in turn require, as inputs, accurate geologic characterizations. We investigate the potential of near-infrared (NIR) spectroscopy through hyperspectral imaging in mapping the spatial distribution of organic content at the core-scale with O(100μm) resolution. We apply the method to the immature oil shale of the Green River Formation, USA. We also draw comparisons with a recently developed optical method for detecting kerogen content in organic-rich shales [1]. Implications for mapping spatial distributions of thermo-hydro-mechanical properties of petroleum source rocks on excavated cores are discussed.
Quantification of organic content (TOC) in unconventional resources is important for both reserve estimation and resource development. There are several methods for measuring TOC, directly or indirectly, which include chemical analysis, Rock-Eval pyrolysis, and well logging [2]. Most of these approaches are often destructive, require careful sample processing, or are limited in spatial resolution. An attractive alternative is spectroscopy, the deduction of TOC from interactions of light of a certain wavelength with the source rock, which is rapid, non-destructive, and potentially requires minimal sample preparation.
In geosciences, two regions of the electromagnetic spectrum are used for quantifying the abundance of minerals and organic matter. The first is the mid-infrared (MIR), which spans wavelengths between 2500 and 25000nm. The other is the near-infrared (NIR) spanning wavelengths between 1000 to 2500nm. Reflectance, a (mostly) material property measured in spectroscopy, is defined as the ratio of the intensity of light reflected from a sample surface to the intensity of the incident light of a given wavelength.
