Simulation of Surfactant Oil Recovery Processes and the Role of Phase Behaviour Parameters

Chemical Enhanced Oil Recovery (cEOR) processes comprise a number of techniques which modify the rock/fluid properties in order to mobilize the remaining oil. Among these, surfactant flooding is one of the most used and well-known processes; it is mainly used to decrease the interfacial energy between the phases and thus lowering the residual oil saturation. A novel two-dimensional flooding simulator is presented for a four-component (water, petroleum, surfactant, salt), two-phase (aqueous, oleous) model in porous media. The system is then solved using a second-order finite difference method with the IMPEC (IMplicit Pressure and Explicit Concentration) scheme. The oil recovery efficiency evidenced a strong dependency on the chemical component properties and its phase behaviour. In order to accurately model the latter, the simulator uses and improves a simplified ternary diagram, introducing the dependence of the partition coefficient on the salt concentration. Results showed that the surfactant partitioning between the phases is the most important parameter during the EOR process. Moreover, the presence of salt affects this partitioning coefficient, modifying considerably the sweeping efficiency. Therefore, the control of the salinity in the injection water is deemed fundamental for the success of EOR operations with surfactants.