Molecular Insights into Organic Matter–Mineral Composite Mechanical Behavior: Implications for Subsurface Reservoir Stimulation and Storage Operations

Shale gas production relies on stimulation techniques that fracture the rock to enhance gas flow. The success of these techniques hinges on the complex interplay between the induced stresses and the inherent mechanical response of the shale itself. This response is heavily influenced by the intricate mosaic of minerals, clays, and organic matter within the shale formation. This study bridges a crucial knowledge gap by investigating the mechanical behavior of organic matter, a key yet understudied component, and its interactions with inorganic minerals at the interface using molecular simulations. Two kerogen models (immature—II-A and overmature—II-D) were constructed and their mechanical properties were assessed. The results revealed ductile behavior with both elastic and plastic regions during deformation. Additionally, the influence of organic matter maturity on interaction strength with minerals (quartz and calcite) was explored. The simulations suggest a preference for calcite at the interface, with stronger attractions observed for the immature kerogen (II-A) compared to the overmature one (II-D). The interaction energies ranged from over 600 kJ/mol (attraction) for calcite to less than half that value for quartz, while the corresponding Young’s modulus values fell within the range of 3.27–4.26 GPa. Finally, the impact of CO₂ injection on these interactions and the mechanical response of the composite systems was investigated. The presence of CO₂ did not significantly alter the organic matter–mineral interaction energies and the mechanical failure envelopes. However, stiffness was found to decrease by approximately 9–14%. This research paper unveils the organic matter–minerals behavior from a mechanical perspective at the molecular scale. The reported findings provide insights that could be utilized to optimize stimulation and other geo-storage processes.