Surfactants for enhanced oil recovery

The anionic cocogem surfactant of formula (I) for an oil production process of increased efficiencywhereineach R1 and R2 is independently selected from hydrogen or C1-C18 straight or branched alkyl optionally substituted by OH;each R3 is independently selected from hydrogen; C1-C25 straight or branched alkyl or alkenyl optionally comprising inter-chain amido-group; aromatic group optionally substituted by C1-C25, preferably C5-C20, more preferably C5-C15 straight or branched alkyl, preferably selected from phenyl and diphenylether; or C10-C20 straight or branched alkenyl, alkadienyl or alkatrienyl;Z is C1-C18 straight or branched alkylene optionally substituted by one or two C1-C6 alkyl or preferably C3-C6 cycloalkyl, optionally comprising (EO)n and/or (PO)m groups, wherein EO is ethylene-oxide i.e. -CH2CH2O-, and PO is propylene-oxide, i.e. -CH(CH3)CH2O-, wherein n and m is independently an integer of from 0 to 30 and n+m is an integer of from 1 to 30; and/or [NH(R4)]+ quaternary ammonium, wherein R4 is hydrogen, C1-C6 alkyl, preferably methyl or ethyl;R5 is hydrogen or C1-C6 alkyl, preferably methyl or ethyl;An is one or more groups selected from SO3−, Cl− or CO2−;i is an integer of 0 or 1;p is an integer of 2 or 3;j is an integer of 2 or 3.