| Surfactant is the key technology to improve the oil recovery factor for alkaline surfactant polymer(ASP) and surfactant polymer flooding.In order to substantially lower the capillary resistance of oil drop through the reservoir pore,the key performance of surfactant is to decrease the oil-water interface tension to less than 10-3mN/m.Nowadays,the surfactant, employed in ASP and surfactant polymer flooding is mainly heavy alkybenzene sulfonates (HABS).Although the HABS has good oil-water interfacial active,the supply of the raw material,heavy alkylbenzene,limits its development.Therefore,developing a new surfactant with sufficient raw material and stable quality,which can replace the HABS,becomes a research highlight in petroleum exploration and development field.In this article,the modified sodium petroleum sulfonate(SPS) was synthesized by two residual oils with sufficient raw material,which are furfural extracted oil and the vacuum third line distillate oil of Daqing refining oil company,as raw material and oleum as sulfonated agent. The products realize the ultra oil-water interfacial tension 10-3mN/m under 300mg/L Ca2+ and Mg2+concentrations.The structures of the two products were investigated by characterization methods.The results indicated that the SPS synthesized from the vacuum third line distillate had wide molecular weight distribution,high average molecular weight and can lower the oil-water interface tension.In order to improve the ability of resisting calcium and magnesium ions,a modified SPS were synthesized by two methods with two residual oils as raw material.One is Friedel-Crafts acylation with maleic anhydride and then sulfonation with Na2SO3.The critical micelle concentrations(CMC) and the minimum surface tensions of the two PCS were measured by Wilhelmy plate method.CMC is 1.76×10-3g/L and minimum surface tension is 36.18mN/m for the product of furfural extracted oil.While CMC is 1.02×10-3g/L and minimum surface tension is 38.92mN/m for the product of the vacuum third line distillate.The other is reaction with diethyl malonate by Knoevenagel method,with acyl chloride as acylation agent and then sulfonation with oleum.The surface properties analysis results display that CMC is 1.23×10-3g/L and minimum surface tension is 39.14mN/m for the product of furfural extracted oil.While CMC is 1.09×10-3g/L and minimum surface tension is 43.35mN/m for the product of the vacuum third line distillate.The results indicated that the two synthetic routes are feasible for the two residual oils. The results of magnesium and calcium ions tolerance test indicated that the modified SPS, synthesized from the above two methods,has good chelation with magnesium and calcium ions for the crablike carboxyl and ester group and increase the reaction weight with magnesium and calcium ions for addition of hydrophilic group.Both of the two modified petroleum sulfonates could produce ultra-low interfacial tension at calcium and magnesium ions concentration lower than 600 mg/L,whereas the general petroleum sulfonates could only produce ultra-low value below 300 mg/L.It can be concluded that the SPS synthesized from the residual oil of Daqing refining oil company,which are furfural extracted oil and the vacuum third line distillate,was a kind of low costing and salt resisting surfactants having good ability in lowering interfacial tension for enhanced oil recovery.
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