| 主权项 |
1. An aqueous composition comprising a mixture of:
water, 0.1 to 10 weight % water soluble polymer for forming a viscoelastic gel when in solution in said water when the polymer concentration exceeds a critical gelling concentration, said water soluble polymer having a number average molecular weight of between 5 kg/mol and 20,000 kg/mol, wherein the water soluble polymer consists of at least one member selected from the group consisting of polystyrene-poly acrylic diblock polymers, and 0.08-3 weight % zwitterionic surfactant, selected from at least one member of the group consisting of Erucic Acid Amidopropyl Betaine and Oleoylamidopropyl betaine,
wherein the zwitterionic surfactant is not an amphoteric surfactant, and less than 0.3 wt % each of an anionic surfactant, amphoteric surfactant and nonionic surfactant, and1 to 10 weight % inorganic salt selected from at least one member of the group consisting of monovalent electrolytes, divalent electrolytes and trivalent electrolytes, wherein the monovalent electrolytes have a formula A+B−, wherein A is an alkali metal and B is a halogen,
wherein the divalent electrolytes have a formula Aa+xBb−Y, wherein A is selected from the group consisting of calcium, magnesium, ferrous iron and B is selected from the group consisting of chloride, bromide, sulfate, carbonate, nitrate and a times X is +2 and b times Y is −2,wherein the trivalent electrolytes have a formula Aa+xBb−Y, wherein A is selected from the group consisting of ferric iron and B is selected from the group consisting of chloride, bromide, sulfate, carbonate and nitrate and a times X is +3 and b times Y is −3, and optionally a proppant. |
