Abstract: The invention relates to a treatment fluid for consolidating an unconsolidated or weakly consolidated granular porous substrate without simultaneous substantial loss of permeability and a method for doing the same. According to the invention, the treatment fluid comprises a solvent;—a surfactant, in a concentration sufficient to form admicelles at the surface of grains of the substrate; and—at least one compound comprising a functional group able to polymerise, together, where appropriate, with a polymerisation initiator. The invention can be implemented, in particular, for consolidating sandstone of a rock formation.