The experimental results show that with the osmotic pressure
due to different concentration ratios across the copper hexacyanoferrate membrane, water in low-solute concentration
permeates through the membrane into the high-solute fluid, increase the formation pressure, and extract more oil. Furthermore,
the experiments of wettability alteration showed that the membrane of copper hexacyanoferrate does not change the wettability
of rock. Additionally the rate of EOR was only 0.2% for fractured
rock without copper hexacyanoferrate membrane. Based on these
observations, the essence of applying semi-permeable membrane
technology to increase the oil recovery from fractured reservoir is
to utilize osmotic pressure to increase the formation pressure and
to displace oil in-situ.