## 1 Introduction
The Linear Isotherm model provided acceptable results for surfactant concentrations less than 2 wt%. Alkaline-surfactant (AS) flooding was developed in the 1980s by Shell to overcome the problems of standalone surfactant flooding [4]. The main advantage of AS flooding is the combination of the working mechanisms of each chemical. Specifically, reduced IFT and lower surfactant adsorption are the primary governing parameters for incremental oil recovery by AS flooding [15; 16]. Alkali is a high-pH chemical which can form in situ surfactants in contact with oil's saponifiable components [1; 3]. Sodium hydroxide (NaOH) and sodium carbonate (Na\({}_{2}\)CO\({}_{3}\)) are the most effective alkalis for chemical EOR [17; 18]. For in situ surfactant formation, the oil's total acid number (TAN) is an important parameter to be assessed prior to commencing alkali flooding. According to [PERSON] and [PERSON] [19], the TAN should exceed 0.1-0.2 mg KOH per gram of oil to facilitate an effective emulsification recovery mechanism during alkali flooding. However, recent findings by [PERSON] et al. [20] demonstrate successful ASP applications in fields with even lower TAN, such as the West Salym field in Russia (0.04 mg KOH/g) and the Daqing field in China (0.02 mg KOH/g). [PERSON] et al. [21] also indicated that even in cases of low TAN, a synergistic effect between the injected synthetic surfactants and the in situ surfactants leads to an ultra-low interfacial tension [22]. Additionally, injecting alkali into reservoirs with low TAN is beneficial as alkali helps reduce surfactant adsorption [23]. The adsorption reduction happens because of the increasing pH level of the system. A higher pH increases the negative charge of the reservoir rock and surfactant molecules, so more electrical repulsion between surfactant molecule and reservoir rock occurs [24; 25]. Since alkali is less costly than surfactant, using it even with low TAN crude oil can be economically beneficial as it can significantly lower the surfactant consumption [5; 23]. AS flooding is generally conducted in combination with polymer flooding to improve macroscopic sweep efficiency. However, an efficient screening of surfactant and alkali for an alkaline--surfactant-polymer (ASP) flood recipe governs the success of the EOR project [26; 27]. An ASP pilot project consisting of four injectors and one producer was initiated in Mangala field, India, in 2014 and continued for 10 months [28]. The water cut of the pilot area right before ASP flooding was 92%. The pilot ASP design included injection of 0.5 PV of ASP solution, 0.5 PV of polymer flooding, followed by 0.1 PV chase water flooding. One month after ASP slug injection initiated, the oil cut increased from 10% to 80%, yielding an incremental oil production of 23,000 STB. The cores collected from the pilot area after ASP flooding showed residual oil saturation (S\({}_{\text{or}}\)) in the range of only 5-10% [15; 18]. Similarly, ASP flooding has proved beneficial in Daqing oilfield, China [29; 30; 31] and West Salym oilfield in West Siberia [32; 33]. In all these studies, the successful reduction in S\({}_{\text{or}}\) was specifically due to selection of the best surfactant and the remedies adopted to control its adsorption to make the projects economically feasible. Other than alkali, nanoparticles have also gained popularity as an additive for chemical flooding which is attributed to their surface properties and their ability to control adsorption of chemicals such as surfactant and polymer. Various mechanisms exist through which nanoparticles control the adsorption of surfactants in sandstone reservoirs. One notable observation is that surfactant molecules tend to exhibit higher adsorption on the surface of nanoparticles, mainly because of the presence of stronger hydrogen bonding. Consequently, this leads to a reduced amount of surfactant molecules available for adsorption onto the interface of the rock.