**4. Conclusion**

A large amount of gelling polymer systems applicable for the conformance-improvement treatment of heterogeneous oil reservoirs is commercially available or under academic development.

Choosing the most suitable hydrogel for a conformance problem should be done taking into account the temperature, salinity, and hardness of the reservoir, as well as the pH of the injection water.

Other parameters that should also be considered are the presence of carbon dioxide (CO<sup>2</sup> ) or hydrogen sulfide (H<sup>2</sup> S), the adsorption of the chemicals on reservoir rock, the permeability of the target region, reservoir mineralogy and lithology, as well as toxicity and cost of the gelling system components.
