Optimization The effect of waterflooding in chalk reservoirs

It is experimentally documented that seawater with increased amounts of the potential determining ions, SO4 2-, Ca2+ and Mg2+, can significantly improve the oil recovery in chalk reservoirs at high temperatures. Usually, wettability alteration is reported as the main mechanism for the improvement in oil recovery. Our recent study proposed that the decrease in viscosity and formation of an emulsion phase could also be a possible reason for the observed increase in oil recovery. It was found that two crude oils exhibited different phase behavior and viscosity variation in contact with the same brine solutions. In this work, we study crude oil/brine interactions further: We investigate the effects of compositional differences of crude oils and also study heptane/seawater interactions under different temperatures, pressures and sulfate ion concentrations. For the two crude oils studied, the heavier oil (that with a large fraction of heavy components) exhibited viscosity reduction in contact with brine, while the lighter crude oil exhibited emulsion formation. We have also observed formation of an emulsion phase in the heptane/brine systems under high pressures and temperatures. It is concluded that viscosity reduction for a crude oil in contact with brine is connected to the presence of heavy components in the crude oil, while formation of emulsions with brine is a phenomenon related to the presence of lighter components in the crude oil

کلیدواژه ها:

Water flooding ، oil recovery ، crude oils ، heptane ، viscosity ، emulsification ، emulsion ، phase behavior