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 core flood experiments used Berea core material and all cores were aged at 90C for more than three weeks using a crude oil with high acid number. 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 weterflood are discussed in relation to fines migration, mixed wet particle flow, microscopic diversion, surface interactions, and possible wettability alteration. This study is using two somewhat different approaches (ECLIPSE and UTCHEM) to model the extra oil produced by lowering brine salinity and also for modelling the surfactant injection. The main assumptions of both of the applied models are shift in relative permeability to more water wet with lowering of brine ionic strength. 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.
展开▼
