We study the physical mechanisms of fluid-driven fracture in low permeability reservoirs. This is done through the use of laboratory scale experiments on brittle heavily cross-linked hydrogels. These hydrogels have been shown to fracture similarly to ‘standard’ brittle materials, which have been widely used to model geological mechanics. Crucially, the hydrogels are transparent, and permit fracturing at lower pressures and slower timescales. In particular, we will discuss fracturing regimes in which either viscous energy dissipation or material toughness dominates the rate of crack growth. Scaling laws for these regimes will be presented and matched against our experimental

Keywords: Geophysical flows, Experimental techniques, Applied fluid dynamics