Abstract: The invention concerns a method and a system for predicting the apparent flow conductivity of a heterogeneous medium. According to the invention, the following steps are implemented:—choosing a flow conductivity element type with a given set of characteristic parameters;—determining equations for said flow in said element type;—determining a network statistics for said given set of characteristic parameters; and—performing a stochastic homogenisation of said equations, for said network statistics. The invention applies more particularly to the predicting of the apparent viscosity of non-Newtonian fluids in a heterogeneous porous medium.