The present invention relates to the use of a combination of block polymers and particular compositions in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock following the injection thereof, the combination comprises (i) a polymer comprising: —a first block that is adsorbed on at least a portion of the particles; and —a second block, having a composition different from that of the first, and having a weight-average molecular weight of greater than 10 000 g/mol, for example greater than 100 000 g/mol, and that is soluble in the fluid; (ii) particles suitable for providing a gas barrier effect, preferably a latex and/or silica particles.