## 1 Introduction
Rather, it focuses on the reduction of the melting point of the eutectic, independently of the character of the compounds that are being mixed. [PERSON] et al. [15] were the first authors to propose the use of these chemicals for EOR. Eutectics composed of choline chloride (ChCl) and either glycerol or urea were tested for the application, achieving a respectable level of EOR mainly due to viscosity increase and wettability alteration. However, the high concentration of the eutectic mixture used in the aqueous formulation (50 vol%) would likely render the method economically unfeasible in a practical scale. Mixtures of ChCl and ethylene glycol were proposed by [PERSON] et al. [16], obtaining tertiary oil recoveries in the range of 6% to 16% of OOIP, but again using a concentration much greater (by a factor of ca. 50) than the usual chemical concentrations in EOR. Laboratory-scale screening, based on microemulsion generation, of different chemicals was carried out by [PERSON] and [PERSON] [17]. The 2-hydroxyethyltrimethylammonium chloride + urea, 2-hydroxyethyltrimethylammonium chloride + propenatriol, and sodium carbonate + propenatriol eutectics were found to be unable to form oil-in-water emulsions and discarded for further studies. [PERSON] et al. combined ChCl and malonic acid at two different concentrations, producing 7-14% of the residual heavy oil after brine flooding, and with wettability alteration identified as the dominant mechanism for the oil recovery. They found better performance at higher temperatures [3]. [PERSON] et al. [18] proposed the use of quaternary ammonium-based eutectics for the application. They used molecular dynamic simulation to study interactions between oil and eutectics, and the efficacy of the method was tested experimentally at low scale and by simulation at field scale. Core-flooding tests were carried out by [PERSON] et al. [19] with aqueous formulations (1 vol%) of the ionic liquid 1-dodecyl-3-methylimidazolium chloride and the eutectic formed by choline chloride and citric acid. As in previous cases, the eutectic was not able to reduce the IFT, which is the reason why the authors proposed its combination with a very low concentration of cetyltrimethylammonium bromide (CTAB) as co-surfactant. The ionic liquid performed slightly better than the eutectic-CTAB mixture for EOR. Recently, these authors proposed the use of ionic liquids and eutectic solvents as potential inhibitors to reduce CTAB adsorption [20]. The combination of the chemicals generally used in EOR with the advantages of eutectics may constitute a promising approach, as this would greatly facilitate the preparation of the formulations. Thus, in this work, the use of a eutectic mixture composed of a surfactant and a polymer was proposed for EOR. The traditional anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate, also known as sodium docusate or as AOT, was selected for its capacity to reduce IFT. Polyethylene glycol (PEG) was selected as polymer due to its capacity to form hydrogen bonds, thermal and chemical stability, viscosifying power, low adsorption on rock surfaces, low toxicity, and low cost. Solid-liquid equilibria were studied for the different surfactant/polymer systems, looking for a eutectic behavior. An optimal formulation was defined through the minimization of water/oil IFT by changing salinity. Finally, adsorption tests and a core flooding experiment in sandstone were carried out to analyze the capability of the formulation to extract oil.