Effect of Temperature on Surfactant Adsorption in Porous Media

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Abstract
The effect of temperature on the adsorption of a sulfonate surfactant and a nonionic surfactant onto crushed Berea sandstone was studied by both static and dynamic techniques. Static experiments were conducted over a temperature range from 25 to 95 °C to define temperature-sensitive rock/surfactant systems and to establish the shape of the equilibrium isotherm. Dynamic experiments served to reinforce the findings of the static tests and extended the temperature range for sorption to 80°C. This is a typical steamflood temperature. A mathematical model that incorporates the mass transport, thermal degradation, and rate-dependent adsorption of the surfactant represented these dynamic results. The model was used to determine the effect of temperature on the sorption rate constants. Mineral dissolution at elevated temperatures has been found to cause precipitation of the sulfonate. Adsorption of the nonionic surfactant decreased with an increase in temperature at low concentrations, whereas the opposite was true at high concentrations. This has favorable implications for a low-concentration injection scheme. When performing static adsorption experiments, care had to be taken because of the poor thermal stability of the nonionic surfactant.