海水条件下延展型表面活性剂降低界面张力性能研究

Study on the performance of extended surfactants in reducing interfacial tension under seawater conditions

为系统探究海水条件下延展型表面活性剂降低界面张力的结构-性能关系,本研究选取不同结构的延展型表面活性剂进行了界面张力测试,并分别考察了疏水烷基链长、烷基支链化、氧丙烯(PO)基团数、氧乙烯(EO)基团数对降低界面张力能力的影响。结果表明,通过增加烷基链长和疏水基支链化,对界面张力降低能力影响幅度小,不能达到超低数值(<10^(-2)m N/m)。PO数是影响延展型表面活性剂降低界面张力能力的关键因素,通过长PO链段螺旋卷曲,增大疏水基尺寸,在适宜的亲水亲油平衡条件下,可以将界面张力降至10^(-3)m N/m数量级。EO基团增加不利于分子在界面上紧密排列,造成界面张力升高。原油组分在界面上的竞争吸附不利于界面张力降低,PO数增加,与原油的界面张力逐渐降低。该类表面活性剂在海水条件下依然具有高界面活性,适用于海上油藏化学驱提高采收率。

The aim of this work was to systematically explore the relationship between the structure of extended surfactants and their abilities in reducing interfacial tension(IFT)under seawater conditions.Those extended surfactants with different structures were selected to test IFT.The effects of hydrophobic alkyl chain length,alkyl branching,and numbers of oxypropylene(PO)and oxyethylene(EO)groups on the ability of reducing IFT were investigated.The results showed that by increasing the length of the alkyl chain and the branching of the hydrophobic group,the effectiveness in reduction of IFT was small,which could not achieve the ultra-low level(<10^(-2) mN/m).In contrast,the PO number was a key factor affecting the IFTs of the extended surfactant solutions against hydrocarbons and crude oil.The IFT could be reduced to the magnitude order of 10^(-3) mN/m at appropriate hydrophilic-lipophilic balance by spirally curling the long PO segment and thus increasing the hydrophobic group size.The increase of EO groups lead to incompact arrangement of molecules at the interface,resulting in the increase of IFT.The competitive adsorption of crude oil components at the interface was unfavorable to the decrease of interfacial tension.The increase of PO number lead to the gradual decrease of IFT against crude oil.This extended surfactant showed high interfacial activity under seawater conditions,which was suitable for chemical flooding to enhance oil recovery in offshore reservoirs.