Geomechanics of Organic Matters Contained in Shales: A Molecular-Level Investigation

Petrophysical and mechanical properties of kerogen are difficult to obtain through conventional techniques due to length scale limitations. Characterization of kerogen requires the isolation of organic materials from the rock matrix, which is associated with a high probability of mechanical damage or chemical alteration of the properties. Alternatively, computational modeling and molecular representation of kerogens can be used to simulate the outcomes of the experimental work. Volumetric and thermodynamics modeling of kerogens has provided the means for recreating nanoscale structures virtually. This research implements existing three-dimensional (3D) kerogen macromolecules to form kerogen structures that can be analyzed for the mechanical behavior of type II organic matters, mainly found in shales, at different maturity levels. Additionally, the underlying factors that could control the mechanical behavior, such as the density and porosity, were investigated. The results are compared against those reported following a similar methodology or other advanced fine-scale experimental work. The results revealed an elastomer-like mechanical behavior of kerogen with comparable elastic moduli regardless of maturity level. Moreover, the mechanical behavior of kerogen was sensitive to the type of fluid contained within the structure. Such observations can help shed more light on the macroscopic mechanical properties of shales, especially for formations with high organic contents.