Nanochemomechanics of Shale: Coupled WDS-Indentation Analysis

Abstract

In this study, a novel methodology is implemented to access the in situ chemomechanics of shale at micrometer length scales. To accommodate the highly heterogeneous microstructure of shale, massive grids of coupled wave dispersive spectroscopy (WDS) and instrumented indentation experiments were performed over representative material surfaces. The extensive datasets of compositional and mechanical properties were analyzed using multi-variate clustering statistics to determine the attributes of active phases present in shale at microscales. Our chemomechanical analysis confirmed that the porous clay mechanical phase inferred by statistical indentation corresponds to the clay mineral phase defined strictly on chemical grounds. The statistical indentation and WDS techniques represent a first approach to characterize the chemomechanics of shale at a consistent scale below the macroscopic level. The results represent valuable information for multi-scale modeling of this material, especially for the in situ properties of the porous clay fabric that have been derived thus far only through indirect methods.