Process for recovering oil from subterranean formations

Claim 1

A process for recovering hydrocarbon from a subterranean formation having an injection means in fluid communication with a production means comprising injecting into the formation an aqueous slug comprised of a water-soluvble, substantially linear, high molecular weight polymer obtained by a process which comprises irradiating an aqueous solution having a pH of about 2 to about 12 and containing about 10% to about 40% by weight of: (a) an ethylenically unsaturated monomer having the formula (I): ##STR3## (b) mixtures of monomers of formula (I), or (c) mixtures of at least one of the monomers of formula (I) with up to 50% by weight of an ethylenically unsaturated monomer selected from the group consisting of vinyl sulfonic acid, alkali metal salts of vinyl sulfonic acid, diacetone acrylamide, and mixtures thereof, wherein R represents hydrogen or methyl and Y represents --NH 2 , --OM, ##STR4## wherein M is hydrogen, H 4 N + , alkali metal, or any other cation yielding a water-soluble, polymerizable compound, R 1 , R 2 , and R 3 are 1 to 4 carbon alkyl radicals and X is an anion, and containing at least about 3% by weight of a salt selected from the group consisting of potassium sulfate, potassium chloride, potassium fluoride, potassium bisulfate, tribasic potassium phosphate, dibasic potassium phosphate, monobasic potassium phosphate, sodium sulfate, sodium bisulfate, sodium chloride, tribasic sodium phosphate, dibasic sodium phosphate, monobasic sodium phosphate, lithium sulfate, lithium bisulfate, lithium chloride, ammonium sulfate, ammonium bisulfate, ammonium chloride, tribasic ammonium phosphate, dibasic ammonium phosphate, monobasic ammonium phosphate, ammonium fluoride, aluminum sulfate, aluminum chloride, and mixtures thereof, with high-energy ionizing radiation at an intensity of about 1,000 to about 200,000 rads per hour to a total radiation dose of about 1,000 to about 30,000 rads, to form an aqueous solution of a water-soluble, substantially linear high molecular weight polymer, provided that when the aqueous solution contains at least 3% by weight of a water-soluble salt selected from the group consisting of aluminum sulfate, aluminum chloride, and mixtures thereof, the unsaturated monomer consists of about 5% to about 100% of cationic monomer and about 95% to 0% nonionic monomer, and the aqueous solution has a pH of about 2 to about 5, and provided that the aqueous solution has a pH of about 7 to about 9 when the water-soluble salt is an ammonium salt, and thereafter displacing the aqueous slug toward the production well to recover hydrocarbon therethrough.