Document Type : Research Paper
Today, by using half of the oil reserves of the world, natural production of oil has decreased drastically. Gas and water injection for maintaining reservoir pressure is not responsive for oil production.At first, we dispersed silica nanoparticles in low salinity and after two weeks, there was no change in its stability. Then we mixed the nanoparticles in low salinity. After a while, we found out that nanoparticles are completely dispersed but they have lost stability over time. We added silica nanoparticles with different concentrations (0.1, 0.25, 0.5, 0.75, 1, 2) to change the wettability of silica levels of oil-wet to water-wet and observed that at low concentrations silica nanoparticles do not have much effect but it has been effective in concentrations 0.75 to 1 and in concentrations 1 to 2 it has not had much effect. At last, we found that the reason for this is a force called structural disjointing pressure. After diluting, we added salt waters to oil-wet to reduce wettability and we saw that low salinity has destabilized the disjointing pressure of oil films, it tears them, and it replaces films and result in silica surface water-wet. Finally, the tests showed that the use of silica nanoparticles in high concentrations is highly effective and 20-time low salinity are accountable in low concentrations, high temperatures but combining these two solutions increases their effectiveness, and even at ambient temperatures and low concentrations of silica nanoparticles, we see acceptable oil production.