Foaming formulations for enhanced oil recovery

1. A composition C, suitable as foaming composition, which comprises, within an aqueous medium M:

at least one ethoxylated alkylamine; and

at least one amphoteric or zwitterionic surfactant

wherein the ethoxylated alkylamine has formula (I) below:

where:

n is a non-zero number between 1 and 12;

m is a non-zero number between 1 and 12, the sum n+m remaining below 20;

[A-] is a group comprising an alkyl group, selected from:

an alkyl group R— comprising from 8 to 22 carbon atoms;

or

an ethoxylated alkylamine group of formula:

where:

R′— is an alkyl group, comprising from 8 to 22 carbon atoms;

—R″— is an alkenyl group, a group —(CH 2 ) q —

where q is a whole number between 2 and 5

p is a non-zero number, between 1 and 10

with the sum n+m+p remaining below 20.

2. The composition according to claim 1 , wherein the surfactants present in the composition C are stable at least up to 80° C.

3. The composition according to claim 1 , wherein the ethoxylated alkylamine has formula (Ia) below:

where:

n is a non-zero number between 1 and 12;

m is a non-zero number between 1 and 12, the sum of n+m being between 2 and 8;

[A-] is a group consisting of alkyl group, selected from:

an alkyl group R— comprising from 8 to 22 carbon atoms;

or

an ethoxylated alkylamine group of formula:

where:

R′— is an alkyl group, comprising from 8 to 22 carbon atoms;

—R″ is an alkenyl group, a group —(CH 2 ) q —,

where q is a whole number between 2 and 5, and

is a non-zero number, between 1 and 10.

with the sum of n+m+p remaining below 20.

4. The composition according to claim 1 , wherein the ethoxylated alkylamine has formula (Ib) below:

where:

n is a non-zero number between 1 and 12;

m is a non-zero number between 1 and 12, the sum of n+m remaining below 20;

[A-] is a group consisting of alkyl group, selected from:

an alkyl group R— comprising from 8 to 22 carbon atoms;

or

an ethoxylated alkylamine group of formula:

where:

R′— is an alkyl group, comprising from 8 to 22 carbon atoms;

—R″— is an alkenyl group, a group —(CH 2 ) q —,

where q is a whole number between 2 and 5, and

p is a non-zero number, between 1 and 10,

with the sum of n+m+p between 3 and 6.

5. The composition according to claim 1 , wherein the total concentration of ethoxylated alkylamine is between 0.05% and 2% by weight in composition C.

6. The composition according to claim 1 , wherein the amphoteric or zwitterionic surfactant is selected from alkylamidobetaines, alkylamidohydroxysultaines, alkylbetaines, and alkylhydroxysultaines and mixtures of these compounds.

7. The composition according to claim 1 , wherein the total concentration of amphoteric and zwitterionic surfactants is between 0.05 and 2% by weight in composition C.

8. The composition according to claim 1 , wherein the ratio by weight of the total weight of the ethoxylated alkylamines with respect to the total weight of the amphoteric and zwitterionic surfactants is between 10/90 and 90/10.

9. The composition according to claim 1 , wherein composition C comprises only ethoxylated alkylamines and amphoteric or zwitterionic surfactants as surfactants.

10. The composition according to claim 1 , wherein composition C moreover comprises at least one additional anionic surfactant.

11. The composition according to claim 10 , wherein the ratio of the total weight of the anionic surfactants with respect to the total weight of surfactants present in composition C remains below 50%.

12. A method for enhanced recovery of the oil of a subterranean formation, comprising the following steps:

a composition C according to claim 1 is injected into said subterranean formation through at least one injection well, said composition being in the presence of a gas within the subterranean formation;

then

through at least one producing well, a fluid carrying the oil coming out of the subterranean formation is recovered.

13. The method according to claim 12 , wherein the injecting is into a subterranean carbonate-based subterranean formation.