Abstract: A method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir. The method includes injecting a polymer solution from an injection well (32) into the subterranean reservoir to form a polymer slug in the subterranean reservoir, wherein the polymer slug has a leading front and a trailing rear (48), and a graded viscosity profile which decreases in viscosity from the front of the polymer slug to the rear of the polymer slug. The method additionally includes injecting an aqueous solution (50) from the injection well into the subterranean reservoir following to displace the polymer slug through the subterranean reservoir.

Abstract: The invention relates to a method of storing carbon dioxide in a subterranean formation not containing any hydrocarbons, comprising injecting a surfactant into the subterranean formation, injecting carbon dioxide into the subterranean formation, wherein the surfactant is a compound of formula (I), wherein R1, R2, R3, and R5 are independently a hydrogen atom or an alkyl group, A is an alkylene group, and the total number of carbon atoms in the surfactant compound of formula (I) is from 10 to 24.

Abstract: A method for performing a polymer flood of a hydrocarbon-bearing, subterranean reservoir (5) includes (a) injecting a polymer solution from an injection well (32) into the subterranean reservoir to form a polymer slug (44) in the subterranean reservoir, wherein the polymer slug has a leading front (46) and a trailing rear (48), and an S-shaped graded viscosity profile which decreases convexly in viscosity from the front of the polymer slug to an inflection point and concavely in viscosity from the inflection point to the rear of the polymer slug, (b) injecting an aqueous solution (50) from the injection well into the subterranean reservoir following (a) to displace the polymer slug through the subterranean reservoir.

Abstract: A method of extracting hydrocarbons from a subterranean formation includes injecting a surfactant composition into the subterranean formation and collecting hydrocarbons displaced by the injected surfactant composition. The surfactant composition can have at least one polyamine surfactant compound of formula R1R2NA(RNA)xNR3R4, where x is an integer from 0 to 3, R1, R2, R3, R4 and each R are independently a hydrogen atom or an alkyl group, each A is an alkylene group, and the total number of carbon atoms in the surfactant compound is from 10 to 21. The surfactant composition can include liquid or supercritical carbon dioxide.

Abstract: The invention relates to a method of extracting hydrocarbons from a subterranean formation, comprising: —injecting a surfactant composition into the subterranean formation, and —collecting hydrocarbons displaced by the injected surfactant composition; wherein the surfactant composition comprises at least one surfactant compound of formula (I): wherein x is an integer from 0 to 3, R1, R2, R3, R4 and each R are independently a hydrogen atom or an alkyl group, each A is an alkylene group, and the total number of carbon atoms in the surfactant compound of formula (I) is from 10 to 21. The invention also relates to a composition comprising liquid or supercritical carbon dioxide and at least one surfactant compound of formula (I).