Synthesis And Properties Of Double Hydrophobic Group Substituted Benzensulfonates For Enhanced Oil Recovery

Alkali-surfactant-polymer (ASP) flooding has been proved to be one of the most efficient EOR technologies and suitable for most of oil fields in China. However, the surfactants used in ASP flooding, such as petroleum sulfonates(PS) and heavy alkylbenzene sulfonates(HABS) usually have complicated composition or contain components of unknown structure such that the quality of the product and the properties of the formulations are unstable. On the other hand the conventional surfactants are not suitable as surfactants for EOR due to strongly hydrophilicity. In this paper we try to synthesize two kinds of hydrophopbic surfactants with clear molecular structure, dodecyllauroylbenzenesulfonates (DLBS) and dialkylbenzenesulfonates(DABS), and to examine their properties as EOR surfactant in ASP flooding.The results show that DLBS can be synthesized by reaction of industrial dodecylbenzene with lauroyl chloride in the presence of AlCl3, followed by sulfonation with ClSO3H and neutralization with NaOH. The lauroyl is confirmed to be connected to the para-position of the alkylbenzene by 1HNMR spectrum, and the DLBS synthesized is found to be well soluble in pure water and connate water at 45°C, and is highly surface active as indicated by its low cmc, 1.1×10^-5 mol/L, and lowγcmc, 28.6 mN m^-1. By mixing with relatively hydrophilic heavy alkylbenzenesulfonates at a total surfactant concentration of 5 mM(ca.0.2%), DLBS can reduce Daqing crude oil/connate water interfacial tension to an order of 10^-3 mN/m at 45°C in the presence of 0.5¹.0 wt.% NaOH and 1000 mgL^-1 of polymer. With the NaOH replaced by a gentle alkaline salt, Na₂CO₃, the Daqing crude oil/connate water interfacial tension can also be reduced to ultralow once certain proportion of dodecyldimethylcarboxybetaine is formulated and the concentration of Na₂CO₃ is increased to 1.2².0 wt.%. DLBS is therefore a good hydrophobic surfactant applicable in ASP flooding with either NaOH or Na2CO3 as alkaline agents.Similarly DABS can be synthesized by reaction of industrial alkylbenzene with long chainα-olefin followed by sulfonation and neutralization. By reacting dodecylbenzene with C₁₂α-olefin with AlCl₃ as catalyst followed by sulfonation with ClSO₃H and neutralization with NaOH, one of"DABS"was obtained which was found to be actually a mixture of di-dodecylbenzenesulfonate and mono dodecylbenzenesulfonate due to the low conversion in both the alkylation and sulfonation. This"DABS"which contain approximately 65% mono dodecylbenzenesulfonate and 35% di-dodecylbenzenesulfonate in molar ratio is also highly surface active and can also reduce Daqing crude oil/ connate water interfacial tension to an order of 10^-3 mN/m at 45°C once mixed with HABS(2) in a total surfactant concentration range of 0.1⁰.5wt.% in the presence of 0.5 wt.% NaOH, or in a total surfactant concentration of 0.2wt.% in the presence of 0.4⁰.7wt.% NaOH. Great effort is required to obtain pure DABS and characterize their properties.