Viscoelastic foam system for acidic gas switch, and method and use for improving the recovery factor using the same

A viscoelastic foam system for an acidic gas switch, comprising a pH-switch surfactant, a hydrocarbyl anionic surfactant and water;

• the pH-switch surfactant is at least one of long-chain hydrocarbyl amines;
• wherein the long-chain hydrocarbyl amine is a long-chain hydrocarbyl polyamine compound, the polyamine compound has two or more non-cyclic amine moieties, preferably 2-10 non-cyclic amine moieties, for example, 2, 3, 4, 5, 6, 7, 8, 9 or 10 non-cyclic amine moieties, and the long-chain hydrocarbyl is a saturated or unsaturated aliphatic hydrocarbyl having 11 or more carbon atoms, preferably a C11-C24 aliphatic hydrocarbyl;
• the polyamine compound is composed of a main body and a non-main body,
• nitrogen atoms of said two or more non-cyclic amine moieties, atom(s) or chemical group(s) (for example C1-C5 aliphatic hydrocarbyl) used to connect nitrogen atoms of non-cyclic amine moieties, and hydrogen atoms directly connected to nitrogen atoms of non-cyclic amine moieties constitute the main part of the polyamine compound,
• other atom(s) or chemical group(s) connected to nitrogen atoms of the non-cyclic amine moieties constitute the non-main body of the polyamine compound;
• nitrogen atoms of the non-cyclic amine moieties are present in the form of tertiary amine, and primary amine and/or secondary amine (preferably, the tertiary amine comprises 30-100%, e.g. 50%-100%, 90%-100%, or 100% of the total of the primary amine, the secondary amine and the tertiary amine, on the basis of nitrogen atoms);
• the non-main part of the polyamine compound includes or consists of the following (2) and/or (3), and (1):
• (1) at least one, preferably one long-chain hydrocarbyl such as C11-C24 aliphatic hydrocarbyl connected directly or via a linking group to the nitrogen atom of non-cyclic amine moiety, more preferably, the long-chain hydrocarbyl such as C11-C24 aliphatic hydrocarbyl is connected directly or via a carbonyl group (—CO—) to the nitrogen atom of non-cyclic amine moiety;
• and
• (2) at least one C1-C3 aliphatic hydrocarbyl or substituted C1-C3 aliphatic hydrocarbyl directly connected to the nitrogen atom of the non-cyclic amine moiety;
• and/or (3) at least one —(C2-C3alkyl-O—)s—Rs directly connected to the nitrogen atom of the non-cyclic amine moiety, s is 1-60, for example 1-6, or 1-4, or 1-3, or 1-2, Rs is H or an aliphatic C1-C3 hydrocarbyl or a substituted aliphatic C1-C3 hydrocarbyl, —(C2-C3alkyl-O—)s—Rs, e.g. —(C2H4O)sH, s is defined as above;
• the non-main body of the polyamine compound, e.g. at the end of the non-main body of the polyamine compound, does not include ionic group(s), e.g. acid group(s) (e.g. sulfonic acid group, carboxylic acid group, phosphoric acid group, and phosphonic acid group) or salt group(s) (e.g. sulfonate group and carboxylate group, e.g. sodium sulfonate) or quaternary ammonium base group(s) (e.g. betaine and derivatives thereof, e.g. alkyl betaine, alkylamido betaine, sulfopropyl betaine, hydroxy sulfopropyl betaine, and betaine phosphate).