Adsorption and precipitation behaviour of petroleum sulfonates from Saudi Arabian limestone

The adsorption behaviour of a petroleum sulfonate (TRS10-410) on Saudi Arabian limestone has been studied as a function of salinity, surfactant concentration and pH. The adsorption data on limestone exhibit the significant effect of mineral solubility in controlling the surfactant depletion. Release of Ca²⁺ ions from the semi-soluble limestone matrix produces precipitation of the surfactant followed by its redissolution at concentrations exceeding the critical micelle concentration (CMC). This characteristic behaviour generates an apparent adsorption maximum which is of considerable interest in surfactant flooding. The precipitation tolerance of TRS10-410 has also been investigated in the presence of Na⁺ and Ca²⁺ ions to quantitatively describe the precipitation behaviour of this surfactant. The adsorption and precipitation data are analyzed to elucidate the mechanism of surfactant adsorption on limestone and that of surfactant precipitation by inorganic ions.