Ultra-high salinity surfactant formulation

A method of enhanced oil recovery, comprising:

• obtaining a concentrate comprising a water solution of a surfactant having the general structure R1JA, wherein R1 is a C8-C18 primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)x(EO)y(BO)z], wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A is an anionic group, a co-surfactant having the general structure (R2)q(B)Ph-L-Ph(D)(R3)r, wherein R2 and R3 are each, independently in each instance, a C8-C24 linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH2, and an alkoxy alcohol;
• forming an enhanced oil recovery well injection composition by mixing the concentrate with untreated well brine having total dissolved solids of about 100,000 ppm of more and hardness of about 4,000 ppm or more;
• and
• injecting the enhanced oil recovery well injection composition into a well.