Abstract
We performed scaled laboratory experiments of hydraulic fracture propagation and closure in soft artificial rock and outcrop rock samples. We also performed numerical simulations of the fracture behaviour in plastic rocks, using independently measured rock properties. The simulations aided us in interpreting the measurements and extrapolating the results to field scale. Plasticity induces a larger width for a given net pressure, compared with elastic rock. However, the pressure to propagate fractures is only marginally increased and in the case of the laboratory tests was actually lower than expected from elastic behaviour. The most dramatic effect of plasticity is that closure is much lower than the confining stress due to strong stress redistribution along the fracture.
