Development of a novel temperature-resistant and salt-resistant double-cationic surfactant with ?super thick hydration layer? for clean fracturing fluid

In recent years, cationic surfactants have received extensive attention in cleaning fracturing fluid thickeners due to various unique properties. At the same time, the development of temperature-resistant and salt-resistant clean fracturing fluid is the key to deep well oil and gas resource development. In this study, the rigid-soft combined strategy is adopted for molecular structure designs. N,N-dimethylcyclohexylamine and epichlorohydrin are used as the initial reactants; after the ring-opening reaction occurs, they are quaternized with erucamide propyl dimethyl ammonium to synthesize a novel double-cation viscoelastic surfactant, SY?JS. With double-cationic charges on the head group, water molecules are selectively adsorbed around the cation lattice to increase the hydration layer, and thus, salt tolerance is improved. Cyclohexane with a rigid structure improves temperature resistance. The ultra-long unsaturated hydrophobic tail imparts excellent heat tolerance and dissolubility to the designed viscoelastic surfactant. The clean fracturing fluid prepared by 3 wt% SY?JS with 130,000 ppm NaCl or KCl performs well under a shear rate of 170 s-1 at 140 ?C, and the apparent viscosity remains above 30 mPa s-1 after 120 min.. Additionally, the results show that single-tail surfactants exhibit excellent performance at approximately 140 ?C. Afterward, the brine produced from Rumaila and Jiyuan oil fields is used to prepare brinebased clean fracturing fluids, and evaluations, including proppant suspension, gel breaking, and permeability damage, were conducted. The results show that the brine-based clean fracturing fluid completely meets the requirements of hydraulic fracturing industrial application.

Automated summary

In this study, a novel double-cation viscoelastic surfactant was designed using a rigid-soft combined strategy, showing excellent temperature and salt resistance. Experimental results demonstrate that the surfactant performs well in cleaning fracturing fluids for deep well oil and gas extraction.