Simulation of three-dimensional viscoelastic deformation coupled to porous fluid flow

The mechanics of fluid expulsion is essential to the understanding of lithospheric processes. In particular, the transfer of fluids in the deep earth can be responsible for a variety of phenomena from fluid and mass transfer to fluid-enhanced deformation. We present model results of the deformation of fluid-filled viscoelastic porous media in two (2D) and three dimensions (3D). The employed mathematical model is based on Biot's poroelastic theory, extended to account for viscous deformation and plastic yielding during decompaction. As a numerically challenging example we consider the dynamics of spontaneous channel formation in fluid-filled viscoelastic porous media. The modelling results exhibit the impact of decompaction weakening on the formation of three-dimensional solitary-wave-like moving porosity channels in agreement with previous studies. Additionally, the velocity of these channels is higher for low solid viscosities. However, the 3D morphology of such channel-like features, as revealed by new 3D calculations, is finger-like rather than planar-fracture like. More importantly, the particular 3D morphology results in order of magnitude increase of fluid expulsion rates when compared to 2D simulations. The inherent 3D geometry of the process and the resulting high fluid-expulsion rates require high spatial and temporal resolution in numerical models.