Fracture Toughness and Surface Energy Density of Kerogen by Molecular Dynamics Simulations in Tensile Failure

Abstract

Fracture toughness and surface energy density are critical parameters in the simulation of hydraulic fracturing in shale formations. In this study, a microscopic insight into the mechanisms of tensile failure in kerogen is advanced by molecular dynamics simulations for the first time. The elastic properties, critical stress, surface energy density, and fracture toughness of kerogen are analyzed systematically. Our work reveals that kerogen is potentially a weak component in shale, which may serve as a region of fracture initiation and preferential fracture propagation path. The critical energy release rate Gc is higher than the doubled surface energy density γs (Gc ≥ 2γs), which indicates that there may be pronounced plastic deformation in kerogen in the tensile failure. This work sets the stage for the determination of various shale mechanical properties and surface energy density to examine fracturing effectiveness in shale media from the molecular scale.