Oil-displacing aqueous solution thickened with reservoir-tailored block copolymer

Claim 1

In a process for displacing fluid in a subterranean reservoir by injecting a thickened aqueous solution into the reservoir, the improvement which comprises: forming the solution by dissolving a substantially water-soluble linear block copolymer in an aqueous liquid in a concentration, of from about 10-10,000 parts of polymer per million parts of liquid, that yields a selected solution viscosity at the reservoir temperature; using as the dissolved block copolymer one which contains relatively water-soluble polymer blocks (A) and relatively water-insoluble polymer blocks (B) in a B-A-B sequence with the average molecular weight of the water-soluble blocks of the block copolymer being from about 100,000 to 2,000,000 and the average molecular weight of the water-insoluble blocks of the block copolymer being from about 1,000 to 10,000 and with the compositions and proportions of the polymer blocks being such that the molecules of the block copolymer have a selected degree of shear and chemical stability at the reservoir temperature; said relatively water-soluble polymer blocks being sulfonated polyvinylarene blocks and said relatively water insoluble polymer blocks being alpha-olefin elastomeric polymer blocks; and injecting the solution into the reservoir at a rate at which the solution viscosity is substantially undiminished due to a shear-degradation of the molecules of the block copolymer.