Modelling of Hybrid Waterflood EOR Processes

Abstract

Core flood studies have been made to investigate the effect of change in brine salinity on oil recovery from waterflood, and in particular the combination of lowered salinity and surfactant flooding. The experiments have shown a large increase in oil recovery with a surfactant that only lowers the interfacial tension to about 10-2 mN/m. The oil recovery and differential pressure from low salinity waterflood are modelled by change in wettability, defined by change in capillary pressure and water-oil relative permeability. This study has combined modelling of extra oil produced by lowering brine salinity and also by surfactant injection. The main assumptions of both of the applied models are shift in relative permeability due to salinity change and due to increase in capillary number. These processes are partly going on simultaneously which creates challenges to the simulation approach. The mechanisms of low salinity injection and surfactant flooding at low salinity will be discussed in relation to experimental observations and history match of the core floods. Similarly combined low salinity and polymer flooding is showing addition oil recovery even for polymer injected after low salinity injection. Especially in linear core flood experiments the added oil recovery is surprising as the residual oil saturation is expected to be unchanged. The hybrid polymer low salinity process is modelled both by conventional approach and using more advanced methods. The more advanced methods is needed to history match core flood results.