The Effects of Di- or Polysulfonates on Adsorption of Petroleum Sulfonates

Petroleum sulfonates was separated into several fractions with conventional extraction method according to the polarity of extraction solvent. The relative content of mono-, di-, or polysulfonates in each fraction was determined by using high pressure liquid chromatography and then the average sulfonic amount of each fraction can be calculated according to above results. The equivalent weight of each fraction was measured by both two-phase titration method and ESI-MS method, and the results shows the tow methods are comparatively coincident. Furthermore, the mean molecular weight of each fraction can be calculated with the average sulfonic amount and the equivalent weight. Adsorption isotherm and coreflooding adsorption test were both conducted to determine the adsorption amount and adsorption rate of each fraction. It was found that the fraction with the minimum equivalent weight is middle mean molecular weight and its adsorption amount on reservoir sand is maximal. Moreover, two fractions have a tendency to come to saturated adsorption in coreflooding adsorption test, but the time needed for saturated adsorption is distinctly different. However, the total adsorption amount of the other fractions keeps increasing at all time. The mechanisms accounting for the difference of adsorption performance were proposed on the basis of the diverse composition of the fraction.