Patent ID: 9598629
Date: 2017-03-21
CPC Classifications: C09K,E21B

Claim:
1. A process of enhanced oil recovery by surfactant flooding from an oil reservoir of an underground formation comprising the steps of: introducing into the oil reservoir a fluid comprising at least an aqueous medium and at least one water-soluble anionic surfactant, introducing into the oil reservoir at least one nonionic surfactant, being injected in aqueous solution, selected from the compounds of formula (I) below: in which: R is a dodecyl group —(CH m is a number ranging from 0 to 20; n is a number greater than m and between 5 and 40; for inhibiting the anionic-surfactant retention phenomena in the oil reservoir, in which, the nonionic surfactant compound of formula (I) is introduced by at least one of the steps selected from the group consisting of: introduced at least partly in combination with said anionic surfactant as an anti-retention agent for said anionic surfactants; introduced as a sacrificial agent at least partly prior to said anionic surfactant to prevent the anionic surfactant retention effect; and introduced subsequently to said anionic surfactant as an anti-retention agent for said anionic surfactants; after said introducing of the anionic and nonionic surfactants fluid conveying the oil and the anionic surfactant leaves the underground formation.