Geometry of elastic hydrofracturing by injection of an over pressured non-Newtonian Fluid

TL;DR

This study investigates how non-Newtonian fluid injection causes various fracture types in elastic gels, revealing complex fracture behaviors influenced by viscoelastic properties and strain rates, challenging simple elastic theory predictions.

Contribution

It provides experimental evidence of complex fracture patterns, including type II and III fractures, caused by non-Newtonian fluids in elastic media, highlighting the influence of viscoelasticity and strain rate.

Findings

Observation of type II and III fractures

Fracture shape depends on viscoelastic properties

Secondary fractures nucleate under certain conditions

Abstract

The nucleation and propagation of hydrofractures by injection of over pressured fluids in an elastic and isotropic medium are studied experimentally. Non-Newtonian fluids are injected inside a gelatine whose mechanical properties are assumed isotropic at the experimental strain rates. Linear elastic theory predicts that plastic deformation associated to breakage of gelatin bonds is limited to a small zone ahead of the tip of the propagating fracture and that propagation will be maintained while the fluid pressure exceeds the normal stress to the fracture walls (Ch\'avez-\'Alvarez,2008) (i.e., the minimum compressive stress), resulting in a single mode I fracture geometry. However, we observed the propagation of fractures type II and III as well as nucleation of secondary fractures, with oblique to perpendicular trajectories with respect to the initial fracture. In the Video (http://hdl.handle.net/1813/14122) experimental evidence shows that the fracture shape depends on the viscoelastic properties of gelatine coupled with the strain rate achieved by fracture propagation.