ABSTRACT Two gelling systems involving a thermally stable biopolymer-namely, polysaccharide G- and two different crosslinkers-namely, X-linker A and X-linker B- have been tested in the lab for water control applications. The methodology involved tube tests to check the phase diagrams, kinetics and stability of the gel under various temperature, salinity and pH conditions. The gel formed with X-linker B was shown to be much more stable and easier to control than the gel formed with X-linker A. With the X-linker B / Polysaccharide G system, at neutral pH, the kinetics of gelation was extremely slow at room temperature, but quicker above 70°C. Such a system can thus be mixed in surface facilities without any risk of premature gelling and behaves like a single polymer solution during the injection phase. In high-permeability cores, the weak gel formed with X-iinker B / Polysaccharide G was shown to induce a drop in the relative permeability to water an order of magnitude greater than the single polymer, while maintaining very good permeability to oil.