Mechanism of pressure propagation and weakly compressible homogeneous and heterogeneous thixotropic gel breakage to study flow restart

Abstract

Pressure propagation in the soft gels is commonly considered either in terms of acoustic waves or gel degradation. However, in a complete description, acoustic, viscous and gel degradation effects should all be considered simultaneously. Here a creep model is discussed with a suitable time scale. The model predicts a specific mechanism of pressure propagation, indicating that gel behaves like a creeping fluid rather than a fluid shearing only above a critical yield stress. The characteristics of pressure propagation can be used to distinguish between creeping and yield stress fluid. The presented results provide a new physical interpretation of recent experimental data. It is also shown that heterogeneity in the gel can cause center-core cohesive failure, as opposed to the near-wall failure which occurs in homogeneous gels.