  We present a model of the hydraulic fracturing of heterogeneous poroelastic
media. The formalism is an effective continuum model that captures the coupled
dynamics of the fluid pressure and the fractured rock matrix and models both
the tensile and shear failure of the rock. As an application of the formalism,
we study the geomechanical stress interaction between two injection points
during hydraulic fracturing (hydrofracking) and how this interaction influences
the fracturing process. For injection points that are separated by less than a
critical correlation length, we find that the fracturing process around each
point is strongly correlated with the position of the neighboring point. The
magnitude of the correlation length depends on the degree of heterogeneity of
the rock and is on the order of 30-45 m for rocks with low permeabilities. In
the strongly correlated regime, we predict a novel effective fracture-force
that attracts the fractures toward the neighboring injection point.
