Microemulsões e nanoemulsões com constituintes Álcali-Surfactante-Polímero aplicados na recuperação avançada de petróleo

Abstract

The primary and secondary oil recovery can only extract, on average, 30 % of the oil discovered, so it is important to apply advanced oil recovery (EOR) to increase the productivity of the reservoirs. Among the special methods of oil recovery, we emphasize the chemical method in which components such as surfactants, microemulsions, polymers and alkaline solutions are injected with the intent of increasing and facilitating the displacement of the oil from the reservoir rock. The combination of polymer, surfactant and alkali on the same fluid bank known as the alkali-surfactant-polymer method (ASP) has favorable characteristics for EOR application. In this work, microemulsified and nanoemulsified multicomponent systems with ASP constituents were developed for application in the inversion of reservoir rock wettability and EOR. By means of the pseudo-ternary diagrams obtained in the aqueous phase rich region, a microemulsion point (WIV) was selected, with the following composition: 15 % C/S (C/S ratio of 0.5), 0.5 % OP and 84,5 % AP, with distilled water or 1.5 % alkali solution. The sodium carbonate was used as an alkalizing agent and subsequently 0.6 % of three commercial polyacrylamide polymers in the aqueous phase were applied to obtain new microemulsions. With the ASP microemulsion points, by the dilution method, nanoemulsions were formulated with low concentrations of inputs, containing 1.5 % C/S, 0.05 % OP and 98.39 % AP containing 1.5 % Na2CO3 and 0.06 % polymer. The microemulsions and nanoemulsions were characterized by the mean droplet diameter, the maximum size and shape of the micellar aggregates, potential of hydrogen, surface tension, viscosity and rheological behavior using mathematical models and, finally, applied in the inversion of wettability and EOR in Botucatu sandstone. The droplet sizes showed characteristic values of micellar aggregates, the maximum dimension was 4.2 nm and the micelles formats were oblate ellipse, sphere and hollow sphere. The pH confirmed an alkaline value (pH of 10.0 ± 0.5) and the surface tension was reduced, with values below 35.0 mN/m at 25 ± 1 ° C. For the microemulsions without polymer and the nanoemulsions the rheological behavior was newtonian type, and for the others microemulsions the mathematical rheological model was of non newtonian fluids. The viscosity of the microemulsions with polymers were from 19 to 41 cP at 25 ± 1 °C, all higher than the average oil (29.3 °API) present in the Botucatu sandstone, which presents a value of 14.5 cP. All the formulated systems left the rock water wettable, being efficient in the inversion of wettability, favoring the dislodging of the oil. The recovery results have proven the efficiency of sweeping and displacement of microemulsions and nanoemulsions, providing total oil recoveries range from 65 % to 97 %.