Surfactants for enhanced oil recovery

An anionic cocogem surfactant according to the general formula (I) for an enhanced oil recovery process

• wherein
• each R1 and R2 is independently selected from the group consisting of hydrogen and straight or branched chain alkyl having from 1 to 18 carbon atoms, optionally substituted with hydroxy;
• each R3 is independently selected from the group consisting of hydrogen;
• straight or branched chain alkyl or alkenyl group having from 1 to 25 carbon atoms, optionally containing an interchain amido group;
• an aromatic group optionally substituted with straight or branched chain alkyl having 1 to 25 carbon atoms, said aromatic group selected from the group consisting of phenyl and diphenyl ether;
• and a straight or branched alkenyl, alkadienyl or alkatrienyl group having 10 to 20 carbon atoms;
• Z is a straight or branched chain alkylene group having 1 to 18 carbon atoms, optionally substituted with one or two alkyl having 1 to 6 carbon atoms, or cycloalkyl having 3 to 6 carbon atoms, optionally containing (EO)n and/or (PO)m groups, wherein EO is ethylene oxide, that is —CH2CH2O—, and PO is propylene oxide, that is —CH(CH3)CH2O—, wherein n and m are independently integers from 0 to 30 and n+m is an integer from 1 to 30;
• and/or [NH(R4)]+ quaternary ammonium, wherein R4 is hydrogen, alkyl having 1 to 6 carbon atoms;
• R5 is hydrogen or alkyl having 1 to 6 carbon atoms;
• An is one or more groups selected from the group consisting of SO3−, Cl− and 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;
• with the provisos that
• when
• R1 and R2 are both H;
• and
• Z is (PO)m—CH2, wherein m is 1 to 5, and
• i is 0;
• and
• R5 is methyl;
• and
• An is SO3−;
• then R3 is other than the following group
• and when Z is a straight chain alkylene group having 1 to 18 carbon atoms then in at least one occurrence R5 is alkyl having 1 to 6 carbon atoms.