Cleavable surfactants which may be useful in viscoelastic compositions for oil-field applications

摘要

Cleavable surfactants of formulae 1, 2 or 3 in which R1 is an optionally unsaturated, optionally branched aliphatic chain of at least 18 carbon atoms, X is an OCO, CO2, NR7CO or CONR7 group, m is at least 1, Y is NR2R3R4, R2, R3, R4, R5, R6 and R7 are each independently H or a saturated aliphatic chain which is optionally substituted by one or more OH groups with the proviso that in compounds of formula 3 the R group linked to A-is not H. A- is a sulfonate or carboxylate anionic group, Z- is a monovalent or divalent anion and B+ is a monovalent cation or a proton. Surfactants of formula 1 in which X is OCO, R5 and R6 are each hydrogen, m is greater than or equal to 1 but less than 5 and Y+ is NR2R3R4 are specifically excluded, but examples of surfactants given are N,N-dimethyl N-ethyl glycine erucyl ester chloride and monooleyl succinic acid. The surfactants may be useful in the preparation of viscoelastic compositions for oil-field applications, especially for hydraulic fracturing of subterranean formations. They comprise a weak chemical bond which may be broken under appropriate conditions to produce oil- and water-soluble products which typically have no interfacial properties and surface activity compared with the original surfactant molecule.