Can you please expand on your question a little bit, it difficult to understand what is the primary focus? Is your question: why is SO3- group on the side of polymer is suitable for oil extraction in high salt conditions (not sure what is your definition of high salt though) ?
Uma Nudurupati @ Thanks for your reply. actually i have noticed in different polymers and surfactant having this -SO3 group attached works very nicely in high salinity reservoirs. Because major problems in Oil reservoirs is the temperature and the salts ( NaCl, MgCl2 and CaCl2) which coils the Polymers and hence destroy the problem.And mostly divalent cations salts has the worse effect on polymers.