Effect of water content and hydrostatic pressure on the shear properties of montmorillonite: A molecular dynamics study

XB Zheng and QL Liu and W Lu and HL Sun and DB Li, MATERIALS TODAY COMMUNICATIONS, 45, 112159 (2025).

DOI: 10.1016/j.mtcomm.2025.112159

Montmorillonite, a layered silicate mineral, is commonly encountered in oil and gas and mineral resource development. The shear mechanical properties of montmorillonite are highly sensitive to water content and hydrostatic pressure, which is one of the causes of well wall instability in deep shale oil and gas production. In this study, the evolution of microstructure and shear mechanical behavior of different hydrated montmorillonites under hydrostatic pressure was investigated using molecular dynamics simulations. Simulation results indicated that the higher water content led to higher interlayer spacing and smaller shear strength, with a strain rate of 3 x 10-7 fs-1 for shear tests. That is, the interlayer spacing increased by 27 %, while the shear strength decreased by 59.6 %, when the water content increased from 10 % to 30 % at a hydrostatic pressure of 7 GPa. The shear strength of montmorillonite, depend on the interlayer cohesion, increased by 131.3 % and the number of C...W HBonds increased by 6.4 %, when the hydrostatic pressure increased from 3 GPa to 7 GPa at a water content of 10 %. Additionally, under shear strain, the deformation mode of montmorillonite can be illustrated by a 'stickslip' mechanism. Atoms in interlayer spacing undergo higher deformation during shear deformation compared to these sheets. This study elucidates the microscopic mechanisms of shear deformation in montmorillonite, which is of great significance for the investigation of the mechanical properties of such materials and their application in the drilling of wells in deep shale oil and gas reservoirs.

Return to Publications page