Microporomechanical modeling of shale

[摘要] (cont.) This intrinsic behavior represents the composite response of clay platelets, interlayer galleries, and interparticle contacts, yielding an invariant stiffness with respect to clay mineralogy. The anisotropic nanogranular nature of the porous clay in shale as inferred from nanoindentation is confirmed through micromechanics modeling. The intrinsic anisotropy of the clay fabric is suggested as the dominant factor driving the multi-scale anisotropic poroelasticity of unfractured shale compared to the contributions of geometrical sources related to shapes and orientations of particles. For strength properties, the micromechanics approach revealed that the frictional behavior of the elementary unit of compacted clay is scale independent, whereas a scale effect modifies its cohesive behavior. Having established a fundamental material unit and the adequate micromechanics representation for the microstructure, the macroscopic diversity of shale predominantly depends on two volumetric properties derived from mineralogy and porosity: the clay packing density and the silt inclusion volume fraction. The proposed two-parameter microporoelastic and strength models represent appealing alternatives for use in geomechanics and geophysics applications.

[发布机构] Massachusetts Institute of Technology