2.3. Fluid injection assays
The fluid injection assays were carried out basically by injecting fluids in sandstone cylindrical plugs from the Botucatu formation (Santanna et al., 2009), as seen in Fig. 2. This apparatus has already been successfully used in surfactant flooding experiments (Curbelo et al., 2007). The plugs were isolated with resin and their dimensions were 3.8-cm diameter and 8.7-cm length. Before being submitted to the resin application, the plugs had been calcined at 700 °C for 12 h, with the objective of removing all humidity and improving permeability.