## 1 Introduction  
In recent decades, global energy consumption has increased exponentially due to the rise in population, economic growth, and technological development. According to the U.S. Energy Information Administration, it is estimated that global primary energy consumption will increase approximately 40% between 2019 and 2050 [1]. In this context, petroleum will be needed for many years both as an energy source and as a raw material for many essential products. The rate of discovery of new oil reservoirs is currently declining; therefore, long-term efforts should focus on increasing recovery from already exploited fields [2, 3]. Nowadays, around 90% of the world's oil is extracted by means of water flooding (secondary recovery). However, large amounts of water are required to maintain the pressure gradient inside the reservoir [4]. Additionally, water is far less viscous than crude oil and this can lead to a phenomenon known as viscous fingering. During the water injection process, the displacement front is unstable, with water flowing faster than crude oil and, thus, reaching production wells, while the crude remains in the earth [5, 6]. Furthermore, capillary forces retain crude oil in the rock pores. For these reasons, about two-thirds of the original oil in place (OOIP) remains inside the reservoir after secondary flooding [7, 8]. Enhanced oil recovery (EOR) processes include a wide range of methods that intend to increase the productivity and operative life of oilfields after conventional water flooding. EOR techniques comprise thermal recovery, miscible gas injection, and chemical methods. Among these options, chemical EOR is widely used for low- and medium-viscosity crudes, regardless of the type of rock formation [8]. Polymer flooding is a chemical EOR technique that can improve the sweep efficiency of water by reducing its mobility. Polymers are inexpensive chemicals that can be added to the displacing phase to increase its viscosity and thus reduce the viscous fingering effects [2]. Other chemical agents that are widely used in EOR are surfactants. The main functions of surfactants are the reduction of the water/oil interfacial tension (IFT) and the alteration of the wettability [8]. IFT reduction is the most important mechanism to increase the capillary number and thus enhance oil mobility, allowing it to be flushed out of the reservoir. Ultra-low water/oil IFT values are required to obtain high oil recovery. Besides decreasing the IFT, surfactants can also alter the wettability of the rock towards water-wet by adsorbing on the reservoir surface [9; 10]. Combined chemical EOR methods are being implemented in most cases, since they can exploit the synergy of different substances during the extraction process [11]. In particular, surfactant-polymer (SP) flooding is employed to mitigate the degradation of the surfactant, decrease the aqueous mobility of the formulation, and improve the economics of the process [12]. Therefore, including polymer in a surfactant slug is practically a requirement for maintaining a favorable mobility ratio [13]. The current application of the method involves the manipulation of polymers and surfactants that are often solid at ambient conditions, thus representing an additional difficulty in the preparation of the formulations to be injected. As an advance in the application of the method, the use of eutectics combining these chemicals is proposed for the first time in this work. The term \"eutectic\" is applied to describe an isothermal reversible reaction of a liquid phase that is turned into two or three different solid phases during cooling [14]. In other words, a eutectic is a binary or ternary mixture with a melting point lower than those of the pure components. Recently, (deep) eutectic solvents have received great attention for EOR applications. However, the literature to date on this specific niche of research is very limited and it does not focus on the combination of polymers and surfactants.