Effects of salinity, total flow rate, and gas flow rate on the foam generation using internal olefin sulfonate (IOS) surfactant were investigated. The compatibility tests performed at 1-11% NaCl at a room temperature of 22 °C showed that the volume of foam on the surface of the liquid increased with salinity increase from 1% to 11% NaCl, indicating that the foamability did not reduce but solubility of surfactant in brine decreased with increasing salinity. The surfactant precipitation on the bottom of the test tubes occurred starting from 6% NaCl at 22 °C and from 8% NaCl at 60 °C. However, surfactant emerged to the surface at 9-11% NaCl because of the increased brine density. The foam scans using 0.5% IOS surfactant were carried out at a salinity of 1, 5, and 8% NaCl through an Indiana limestone core sample of 50 mD at 60 °C. Two total flow rates of 0.4 mL/min and 0.3 mL/min, superficial velocities of 4.39∗10-6 m/s and 5.88 × 10-6 m/s, respectively, were used to simulate flow rates typically applied at the oil fields at 400 and 500 psi. Generally, the differential pressure decreased in the order of gas flow rate decrease while apparent viscosity was higher at lower total flow rate. The apparent viscosity at 5% NaCl were higher than at 1% NaCl at 0.3 mL/min and similar or lower at 0.4 mL/min. The shape of apparent viscosity curves changed from typical for shear-thinning fluids at 1% and 5% NaCl to linearly decreasing at 8% NaCl. The typical increase of apparent viscosity in a low flow regime observed by many authors was very gentle because of the low total flow rates compared to that previously published. The fine foam was observed at the outlet of the system at 1 and 5% NaCl at all foam qualities (gas fractions). At 8% NaCl, the foam was observed at 0.3 and 0.4 foam qualities while only bubbles were formed at 0.5-0.9. In a low foam quality regime, the foam viscosity at the outlet of the system indicated by the length of foam drop before fall decreased at increasing gas fraction while the apparent viscosity was constant. This showed that the foam mobility and volumes of arrived foam could be underestimated by using apparent viscosity. The shape of apparent viscosity curves at low total flow rates and difference between actual viscosity and apparent viscosity should be considered in practical use and numerical simulations.
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