Geomechanical modelling of fault-propagation folds: Estimating the influence of the internal friction angle and friction coefficient

Abstract

The interplay between faulting and folding mechanisms has been recognised in extensional and contractional settings. Numerous investigations have documented that the analysis of structural aspects of fault-related folds is important for the exploration and exploitation of hydrocarbon resources and in seismic data interpretation. In this study, we used four series of 2-D elastic-plastic finite element models (A, B, C, and D) to investigate the influence of internal friction angle, friction coefficient, and an additional detachment on the fault slip and uplift gradients, stress-strain patterns, and structural evolution of fault-propagation folds (FPFs). We found that: 1) the stress-strain patterns are similar in different sections of a FPF; 2) the plastic strain is concentrated at the fault tip, fault surface, and forelimb of the FPF; 3) among the internal friction angle, friction coefficient, and additional detachment parameters, only additional detachment affects the stress-strain patterns at the crest and backlimb of the FPF; 4) to create a FPF, not only must the fault friction be less than the layers, but the layer friction also has to be less than a threshold; 5) increase in the internal friction angle, decrease in the friction coefficient, and generation of an additional detachment lead to the formation of tight folds whereas, decrease in the internal friction angle and increase in the friction coefficient create wide folds; and 6) the internal friction angle and friction coefficient are two key factors of the fault-related fold style.