Crude oil behavior during injection of solutions containing MgSO4in the presence and absence of CO2

Pendant drop method is employed to investigate interfacial tension, bond number, and swelling behavior of crude oil in the presence of brine solutions comprised of MgSO(4)and its solution saturated with carbon dioxide (CO2) (i.e. carbonated MgSO(4)solution) in different temperatures and pressures, up to 80 degrees C and 4000 psi. The results reveal that as the temperature increases, the measured dynamic IFT values getting more close to each other. In detail, the measured dynamic IFT values for the temperature of 30 degrees C are wider than those measured for the temperature of 80 degrees C. Besides, the results demonstrated that not only the dissolution of brine in carbonated brine can reduce the swelling factor which means a barrier against the better dissolution of carbon dioxide into the drop phase but also this salt dissolution can shift the crossover pressure toward the lower values of around 1000 psi from its original value of around 2000 psi. Moreover, examining the effect of pH reveal that at low pH value (i.e., 3.5), a reduction of about 7.6 mN/m in IFT values can be obtained. In sum up, it was deduced that the addition of CO(2)which reduced the acidity of the aqueous phase due to the formation of carbonic acid caused the interruption of ionization of basic natural surfactants, consequently causing a significant diminish of IFT reduction compared to IFT of crude oil/brine solution. In addition, at a constant temperature, the presence of more CO(2)to the aqueous phase at higher pressures leads to IFT reduction as a function of pressure. Moreover, the results confirm that at pressures lower than the crossover point, the effect of temperature variation on the swelling is insignificant but at pressures higher than crossover point swelling factor increases as a function of temperature. Furthermore, the results reveal that the dissolution of salt into the carbonated water reduces the crossover pressure. As the last point, the measured swelling factor revealed that the presence of CO(2)combined with the effect of temperature may lead to an ultimate swelling factor of about 1.32 which means 32% enhancement in the initial volume of the drop oil as it is contacted to the carbonated brine under the temperature of 80 degrees C.