Study of a small molecule gel fracturing fluid and its in situ conversion into an efficient oil displacement agent

Abstract

Viscoelastic surfactants (VESs) are critical components of water-based fracturing fluids. However, the challenges related to the large volumes and complex disposal of flowback fluids from conventional VES fracturing fluids remain unresolved. Accordingly, a multifunctional small molecule surfactant gel was successfully prepared in this study. This system exhibits the capacity of in situ gel-breaking and converting it into an oil displacement agent, thus achieving the goal of no fluid return. The gel was composed of erucic acid amidopropyl betaine (EAPB), oleic acid amidopropyl betaine (OAPB), and a thickening agent, and the system was referred to as EOO. On the basis of this gel system, a series of performance parameters have been evaluated through extensive experiments. The research results demonstrated that this gel exhibits good stability, viscoelasticity, sand-carrying capacity, and remarkable self-repairing ability at high shear rates. Additionally, the gel achieves ultra-low interfacial tension and wetting reversal characteristics, both of which are conducive to enhanced oil recovery. Oil displacement and profile control of the gel were evaluated using single and parallel core flooding experiments. The results indicated that the EOO gel increased injection pressure in high-permeability cores and mobilized residual oil in low-permeability cores, thereby expanding the swept volume and enhancing recovery. The small molecule gel developed in this study which can be converted in situ into an oil displacement agent is a candidate for enhanced oil recovery in low-permeability oil fields.