VISCO-ELASTIC PARASITIC FOLDING: INFLUENCES ON THE RESULTING VOLUMETRIC STRAIN DISTRIBUTION

Parasitic folds represent a common structure of multi-scale multilayer folds and the resulting asymmetric S- or Z-shapes and symmetric M-shapes represent a complex strain distribution. How the strain distribution during the deformation of parasitic fold remains unclear. In this study, a 2-D plane strain finite element modeling approach is used to simulate multi-scale, multilayer, viscoelastic buckle folds under in-situ stress and pore pressure conditions. A variety of material and model parameters (including the elastic modulus contrast, number of layers, viscosity contrast, strain rate and layer thickness ratio) are considered and their influence on the shape of parasitic folds and on the resulting volumetric strain distribution is analyzed. This study demonstrates that the shapes of the parasitic folds depend on the buckling of both the large- and small-scale folds and are influenced by the various parameters. The numerical modeling results show a large variability in volumetric strain during the mutli-scale, multi-layer buckling process. In addition, the numerical simulations provide a general understanding of the influence of the various model parameters on the resulting volumetric strain distribution. Through the applied volumetric strain-porosity-permeability coupling, influences on the resulting fluid flow regimes in multi-scale, multilayer buckling systems are documented.