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Steam injection is widely used as an enhanced oil recovery method for heavy oil fields; however, its efficiency normally decreases in late injection stages. Recent studies have suggested that steam and chemicals together have a potential to increase oil recovery. Despite the use of microemulsion alone has been previously made as a chemical enhanced oil recovery technique, steam and microemulsion alternated injection has not been reported yet. Thus, the present study evaluates this recovery method as an innovative way to optimize heavy oil recovery in sandstone reservoirs. Three microemulsions were produced using Ultranex NP100 (surfactant), n-butanol (cosurfactant), kerosene (oil phase), and synthetic produced water (aqueous phase), by varying surfactant concentrations. The viscosity, stability, surface tension, and interfacial tension of these systems were analyzed and assessed. Berea sandstone was used to represent sandstone reservoirs, in which the effect of microemulsions on rock wettability was measured. Using a coreflooding system, rock plugs were initially saturated with heavy oil (°API 17.1; from Northeast Brazil). Nine enhanced oil recovery tests were performed using steam and microemulsion alternated injection. In the tests, the injection bank order and the surfactant concentration were evaluated. The results showed that the alternated injection of steam and microemulsion achieved recovery factors between 42.79 and 51.23%, which is higher than that by steam injection alone (33.63%). It was observed that oil recovery using steam injection followed by microemulsion showed a better performance due to a higher effectiveness of displacement mechanisms. Steam reduces oil viscosity, while microemulsions decrease interfacial tensions and alter the sandstone wettability. Additionally, oil recovery increases together with the surfactant concentration due to a higher micelle number. Therefore, this study proves that steam and microemulsion alternated injection is a novel and effective method for enhanced heavy oil recovery in sandstone reservoirs.

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Fluids in terms of rheological behavior can be classified into Newtonians and non-Newtonians. Newtonians are fluids that have unique and absolute viscosities, because the ratio between shear stress and shear rate is constant. In the oil industry, most fluids, such as microemulsions, oil and polymeric solutions, do not exhibit Newtonian behavior. To understand the behavior of chemical fluids, it is necessary to analyze some parameters to interpret their properties and applicability. In this context, the present work aims to obtain and characterize microemulsion systems containing Alkali, Surfactant, and Polymer, and verify their applicability in advanced oil recovery. Thus, we obtained five microemulsion systems consisting of saponified coconut oil (surfactant), Butan-1-ol (co-surfactant), kerosene (oil phase), Na2CO3 (alkali), water and different percentages of the polymer. The systems were characterized by analyzes of particle diameter, surface tension, viscosity and rheological behavior using mathematical models. Droplet sizes showed characteristic values of micellar aggregates. Surface tension presented a slight elevation when the percentage of polymer in the microemulsion increased. Through the rheological study, it was possible to observe that experimental values were better adjusted to the Ostwald-de Waele “power-law” model. As the percentage of polymer in the system increased, we calculated the apparent viscosity of the systems and observed an increasing change in viscosity values, a result of great interest to enhanced oil recovery studies.

Fossil fuels, particularly oil, currently dominate the global energy matrix. With a projected 30% increase in demand by 2040 compared to 2010, it is crucial to maintain current oil production levels. To achieve this, it is necessary to increase the oil recovery factor through alternative methodologies that will improve oil extraction from reservoirs and exploration viability in mature fields. While previous studies have investigated thermal and chemical methods to increase the recovery factor, this study aims to explore the synergy between steam and non-ionic surfactants varying the surfactant degrees of ethoxylation and injection configurations. The experimental study investigated the application of solutions of ethoxylated nonylphenol surfactants (NP-10EO and NP-100EO) combined with steam injection into banks at different concentrations and injection configurations. The results showed that combining the NP-100EO surfactant (0.5% m/m) with steam demonstrated the highest oil recovery (64.88%) compared to conventional steam (45.19%). The most effective configurations were surfactant + steam + surfactant (65.06%) and surfactant + steam + water (65.88%). These findings suggest that the proposed technique of steam injection and surfactant solution could be a promising alternative. By revitalizing marginal fields, this technique could help extend production and stimulate local and regional development.

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