Brice Lecampion (EPFL) - Planar Hydraulic Fractures: Theory versus Experiments

Hydraulic fractures are tensile (mode I) fractures propagating under in-situ compressive stresses due to the injection of a fluid at a given rate. In most sedimentary basin, the in-situ stress tensor at depth is sufficiently anisotropic and the maximum stress is vertical. In practice, the created fracture thus propagates in a vertical plane perpendicular to the minimum in-situ stress direction.

In this talk, we will first review the theoretical modeling of the propagation of hydraulic fractures, which combine linear elastic fracture mechanics and lubrication flow. We will notably discuss the competition between the different competing dissipative mechanisms (viscous flow & surface creation) depending on the injection condition. The associated difficulties of the numerical modeling of such moving boundary problem will be briefly highlighted. We will then discuss a series of comparisons between theoretical predictions and laboratory experiments for the initiation and propagation of a hydraulic fracture transverse to a wellbore. We focus on four different laboratory experiments performed in different “tight” materials (Cement, PMMA, Niobrara Shale). In all these experiments, the time evolution of several quantities (fracture width, radius, wellbore pressure) were accurately measured and the material and injection parameters were precisely known. The good agreement between theoretical predictions and experiments provide confidence in the classic hydraulic fracture mechanics models, at least for the simple planar fracture geometry  (pure mode I) and the Newtonian fluids investigated here.

References:

B. Lecampion, J. Desroches, R. Jeffrey, and A. Bunger. Experiments versus theory for the initiation and propagation of radial hydraulic fractures in low permeability materials. Journal of Geophysical Research: Solid Earth, 2017.