Forced folding and fracturing induced by differential compaction during post-depositional inflation of sandbodies: Insights from numerical modelling

Abstract

Three series of numerical models based on the discrete element method were constructed to simulate forced folding and fracturing triggered by postdepositional inflation of fludised sandbody. The models consist of numerous particles that have relatively low to high interparticle bonds to represent overburden sediments with a relatively low to high cohesion, and cohesionless, frictionless particles to represent fluidised sands. The modelling results show that normal faults were produced due to the upward inflation of sand domes and the resulting flexed overburden,

Patterns and Failure Modes of Fractures Resulting From Forced Folding of Cohesive Caprocks – Comparison of 2D vs. 3D and Single-vs. Multi-Layered Analog Experiments

“…Furthermore, the cover is bent upwards and tensile wing fractures open at the base of the cover similar as in our experiments. Numerical models by Meng and Hodgetts (2020) demonstrate the evolution of first tensile and subsequent shear failure dominated deformation of the wing fractures and are therefore in good agreement with our modelling results. If the cohesion is relatively low, in contrast, the cover is vertically displaced due to inflation of the underlying sand or magmatic intrusion.…”

“…( 2) Fracture patterns and opening modes are affected by the rheology of the cover layer and the viscosity of the injected or remobilized fluid (e.g. Montanari et al, 2017;Meng and Hodgetts, 2020), which can be highly variable in nature. Nevertheless, a systematic investigation of the effects of these parameters is beyond the scope of our study, but was qualitatively undertaken by a comparison with previous modelling studies (see below).…”

“…Several analog and numerical models of magmatic and sand intrusion emphasize the effect of the cohesion of the cover layer on fracture modes and the geometry of the forced folds (May et al, 2019;Poppe et al, 2019;Schmiedel et al, 2019;Meng and Hodgetts, 2020). These studies revealed that the forced fold is wider and higher, if the cohesion is larger.…”

“…Brooke et al, 1995;Huuse et al, 2005;Frey-Martnez et al, 2007;Mourgues et al, 2011). At excessive fluid overpressure, the caprock is often uplifted into a forced fold leading to fracturing at the crest and along the hinges of the fold (Cosgrove and Hillier, 2000;Shoulders and Cartwright, 2004;Frey-Martnez et al, 2007;Jackson et al, 2011;Mourgues et al, 2012;Haug et al, 2018;Warsitzka et al, 2019;Meng and Hodgetts, 2020). Depending mainly on the cohesion and the thickness of the cover, these fractures fail in a tensile, shear or hybrid tensile-shear mode (e.g.…”

“…Depending mainly on the cohesion and the thickness of the cover, these fractures fail in a tensile, shear or hybrid tensile-shear mode (e.g. Muirhead et al, 2014;Wilson et al, 2016;Haug et al, 2018;Meng and Hodgetts, 2020).…”