Enhanced oil recovery methods and systems

A method of enhancing the recovery of oil from a subterranean oil-containing formation comprising injecting a viscous aqueous solution containing one or more water-soluble organic polymers into the formation by way of at least one injection well penetrating the formation and forced through the formation towards at least one production well penetrating the formation, and further comprising

• combining water-soluble polymerizable vinyl monomers and a water-soluble ionizing sulfite with an aqueous inorganic salt solution at the site of said injection and production wells whereby said monomers are rapidly polymerized to form a concentrated high viscosity polymer solution, said water-soluble polymerizable vinyl monomers being selected from the group consisting of acrylamide monomers alone, and acrylamide monomers and one or more other vinyl monomers which are copolymerizable therewith;
• diluting said concentrated high viscosity polymer solution with additional aqueous fluid at the site of said injection and production wells to form an injection solution having a desired viscosity;
• and
• injecting said injection solution into said formation.