A model is presented for the propagation of "fractures" in unconsolidated sands. The model departs radically from current models in that brittle fracture mechanics is not used. Instead the propagation of pore pressure is computed and the porosity and permeability of the sand is specified as a function of the effective stress. This results in the creation of an anisotropic zone of increased porosity and permeability along the plane of maximum in-situ stress. This region of enhanced porosity defines a "fracture" in unconsolidated sands. The physics of such a fuzzy fracture is studied for the first time.

The results presented in this paper will have a direct impact on the design and implementation of frac- pack treatments in poorly consolidated sands and provide a basic framework within which to model slurry injection into unconsolidated sands.