Hooked gemini viscoelastic surfactant based on linolenic oil for oil recovery and its various gel-breaking mechanisms

ABSTRACT: Hooked gemini viscoelastic surfactant (HGVES) was designed and synthesized by reactions of linolenic acid with 3-(Dimethylamino)-1-propylamine, 3-Chloro-2-hydroxypropanesulfonic acid sodium salt and isophorone diisocyanate. The structure was characterized by FT-IR and 1HNMR. The properties of HGVES were compared with gemini viscoelastic surfactant (GVES) by surface tension, transmittance, rheological behavior, dynamic light scattering and SEM. The result showed that the fracturing performance of HGVES was superior to that of GVES. The critical micelle concentrations (CMC) of HGVES and GVES were 7.69×10-5 and 9.68×10-5 mol/mL, respectively. Rheological experiments showed that HGVES and GVES were pseudoplastic fluids and HGVES had better viscoelastic behavior. Proppant suspension experiments showed that support suspension performance decreased with the temperature increasing, and the static setting rate was 0.1013 mm/s when the temperature was at 80 °C. Meanwhile, the mechanisms of different gel-breaking agents were also studied, comparing with HGVES and gel-breaking products by FT-IR, 1HNMR, rheological behavior and SEM. The results showed that hydrocarbon oil gel-breaking agents would not destroy the molecular structure of HGVES, while strong oxidant gel-breaking would destroy the double bond of carbon. NaHSO3 would have addition reaction with double bond. The core damage permeability of 2 wt.% HGVES was 5.35%, and there was no residue in all gel-breaking solutions. Therefore, this kind of hooked gemini viscoelastic surfactant can be used in oil fracturing to improve oil recovery.