Research of a fracturing-oil displacement integrated working fluid based on betaine surfactant

With the increasing attention paid to the treatment of flowback fluid, cost control, and environmental pollution in oil reservoir reconstruction and enhanced oil recovery, transforming fracturing fluid into oil displacement working fluid after fracturing has become a solution. In this paper, an EOS gel system is formulated using erucic acid amidopropyl betaine (EAPB), oleic acid amidopropyl betaine (OAPB), and sodium salicylate (NaSal). The system demonstrates high viscoelasticity and achieves ultra-low interfacial tension at low concentrations with dual purposes in fracturing and oil recovery. The comprehensive performance evaluation demonstrates that the EOS integrated working fluid exhibits excellent salt and temperature resistance. The viscosity of 2.8 wt% EOS remains above 24 mPa·s after 1 h of continuous shearing at 80°C. The surface and interfacial tension of the gel breaking solution can be reduced to 26.84 mN/m and 4.54×10-3 mN/m, respectively. The contact angle on the lipophilic glass can be reduced by 22.3°, 22.4° and 21.0° at 60°C, 70°C and 80°C, respectively. Due to the adsorption of surfactant molecules, which reduces the adhesive force of oil droplets and alters the wettability of the rock surface, the static oil recovery rate reaches 19.4% at 70°C, and the dynamic water flooding oil recovery rate can be increased by 11.56%. The fracturing-oil displacement integrated working fluid formulations developed in this paper provides a useful reference for reducing cost to increase benefit as well as enhancement of recovery in the latter period of oilfield development.