2.1. Chemicals
The chemicals used to prepare the microemulsion systems were a commercial anionic surfactant (soap) derived from fatty acids (20–30% of vegetable oil and 70–80% of animal fat, in mass percentages); isoamyl alcohol (C5H11OH, from Merck), used as cosurfactant; pine oil, used as oil phase without previous purification; and distilled water. The petroleum sample used was acquired from the Quiambina field, a mature field located in the Brazilian State of Bahia, and was kindly supplied by the Field-School Project. Also, 2% KCl brine solution was used in conventional injection assays.