A Gemini viscoelastic surfactant stabilized by steric hindrance group on its spacer to construct wormlike micelle structure in concentrated brines

•A steric hindrance group was modified onto the spacer and a salt-tolerant Gemini VES was prepared;•The salinity tolerance mechanism of VES-BC was revealed through a series of experiments;•The WLMs formed by VES-BC exhibit excellent viscoelasticity properties within a wide salinity range. To overcome the disordered aggregation of viscoelastic surfactant (VES) molecules in high concentrated brines resulting in phase separation, a steric hindrance group was modified onto the spacer of a Gemini VES for stabilization in brine, and then a novel Gemini novel VES, named VES-BC, with double erucicamide tails, was synthesized successfully. Molecular dynamic simulation showed that the benzoic acid as a steric hindrance group effectively inhibited the disordered aggregation of VES-BC in concentrated brine, and RDF between the oxygen on the spacer and water varied slightly with increase salinity. Comparably, the Gemini cationic VES without steric hindrance group aggregated excessively and disorderly in high salinity environments, and the counterpart RDF varied significantly. VES-BC exhibits superior stabilization in brines, its salinity cloudy point reaches over 10 wt%. The surface tension, DLS, and fluorescent probe were carried out to explain stabilization mechanism of VES-BC in brine. The wormlike micelle (WLM) construction by VES-BC was studied through viscosity measurement, oscillatory measurement and microstructure observation, which proves the WLM networks can be formed with salinity between 3 wt% and 10 wt%, and 6 wt% is optimal. The steric hindrance group imparts VES-BC an insensitivity to salinity realizing the stabilization in high concentrated brines, and the salinity for WLM-driving is comparably high. Thus, VES-BC is an excellent clean thickener under extremely concentrated brine environment, especially for the preparing of clean fracturing fluid to save freshwater resources.