Abstract

The orientation and spatial organization of hydraulic fractures in rocks and sediments is determined by the magnitude of the differential stress, the orientation of the principal stress axes and the intrinsic properties of the rock, particularly its cohesive strength. Depending on the values of these various parameters the expression of hydraulic fracturing in a rock or sediment can be extremely varied ranging from conjugate shear fractures through parallel tension fractures to randomly oriented tension fractures and fluidized sediments.

The influence of a rock’s properties on its response to hydraulic fracturing is illustrated by considering the mechanics of formation of sedimentary dykes.