Abstract: Hydrocarbons are recovered from a subterranean hydrocarbon-bearing formation penetrated by an injection well and a production well by displacing hydrocarbons toward the production well using a drive fluid such as water thickened with a copolymer of (a) vinyl sulfonic acid alkoxylated with 2,3-epoxy-1-propanol and (b) acrylamide. Optionally, the drive fluid can be saturated with carbon dioxide and/or natural gas at the injection pressure.

Abstract: An oil-based drilling mud which comprises:(a) a hydrocarbon liquid substantially immiscible in water;(b) about 1 to about 100 parts by weight of water per 100 parts of the hydrocarbon liquid;(c) about 2 to about 50 lb/bbl. of at least one emulsifier;(d) about 0.5 to about 5 lb/bbl. of a wetting agent;(e) about 50 to about 750 lb/bbl. of a weighting agent;(f) about 0.1 to about 25 lb/bbl. of a water insoluble, oil soluble terpolymer, said terpolymer having the formula: ##STR1## wherein R.sub.1 and R.sub.3 are selected from the group consisting of hydrogen and a methyl group, wherein R.sub.2 is selected from the group consisting of C.sub.3 H.sub.5, C.sub.6 H.sub.4 --CH.sub.3, C.sub.6 H.sub.4 (CH.sub.3).sub.2 and CnH.sub.2n+1, wherein n=1 to 30 and R.sub.4 is selected from the group consisting of C.sub.5 H.sub.4 N, CnH.sub.2n NH.sub.3 and CnH.sub.2n N(CH.sub.3).sub.