Influence of the mineral composition and pore structure on the tensile mechanical properties of shale from a microscopic perspective: Insights from molecular dynamics simulations

Shale oil and gas—important unconventional hydrocarbon resources—exhibit huge exploration potential. The tensile mechanical properties of shale are crucial for enhancing oil and gas recovery. Herein, molecular dynamics simulations were performed to investigate shale tensile properties. The influence of the mineral composition and pore structure of shale on its tensile mechanical properties and underlying microscopic mechanisms were studied. Results revealed that compared to single-mineral models, composite models generally exhibited considerably lowered tensile strengths (reductions of 47.1 %–98.8 %). However, in the 001 direction, the kerogen–montmorillonite model showed 10.1 % higher tensile strength than montmorillonite. This composite model also showed higher tensile strength than kerogen, exhibiting increases of 157.3 %–1859.6 % in all crystal directions. However, the kerogen–calcite model exhibited 31 % lower tensile strength in the 001 direction than kerogen. An increase in the pore size from 2 to 10 nm resulted in Young's modulus reductions for all minerals by 1.5 %–99.3 % in all crystal directions. Kaolinite exhibited the smallest reduction in Young's modulus in the 100 Crystal directions (1.5 %) and the largest in the 001 Crystal direction (99.3 %). The geometrical control mechanism of pore morphology on damage resistance is decoded, the resistance of different pore shapes to damage varies, demonstrating orientation-dependent failure patterns where slit-shaped pores provide maximum stability in 100 and 010 Crystal directions while triangular configurations dominate in 001 Crystal direction. These findings establish structure-property relationships at the atomic scale that advance fundamental understanding of shale's failure mechanics, while providing engineering-relevant guidelines for predicting hydraulic fracture propagation and optimizing reservoir stimulation strategies.