We investigated the Young’s
modulus and Poisson’s
ratio of Green River oil shale at elevated temperatures under triaxial
conditions using an X-ray computed tomography (CT) scanner for in
situ imaging, fast iterative digital volume correlation (FIDVC) for
visualization of displacement and volumetric strain patterns, and
a conventional linear variable differential transducer (LVDT) to measure
the displacement independently. FIDVC was applied to time-lapse CT
images to visualize the distribution of axial normalized displacement
(U
z
) and volumetric strain
(εV) within the samples at the resolution of the
CT images. Importantly, the displacement obtained by FIDVC was calibrated
and verified with LVDT measurements. Both axial normalized displacement
(U
z
) and volumetric strain
(εV) profiles from the FIDVC method present the location
of greater strains within samples including layered material of greater
density and lesser density organic matter (kerogen and bitumen) rich
zones. The Young’s modulus remained unchanged upon heating
to around 200 °C, but decreased following kerogen maturation
at 350 °C. Young’s modulus decreased at 350 °C due
to rock softening and conversion (maturation) of kerogen to oil or
gas. Accordingly, the fraction of kerogen in a sample plays a critical
role on Young’s modulus. These observations agree with trends
found in the literature (White et al., 2017; Burnham, 2018), but without
in situ imaging. Similarly, Poisson’s ratio did not change
after pyrolysis but increased post maturation.