Laboratory study of the CO₂-responsive clean fracturing fluid

N, N-dimethyl octylamide-propyl tertiaryamine (DOAPTA) was synthesized and then interacted with the anionic surfactant sodium oleate (NaOA), a CO₂-responsive clean fracturing fluid system was obtained. When the mixed solution of DOAPTA-NaOA was prepared at the concentration of 100 mmol/L with the molar ratio of 0.8:1, followed by the introduction of CO₂, the apparent viscosity of solution reached up to the maximum (2.92 Pa·s). Rheological test indicated that the solution system behaved as a viscoelastic fluid, which confirmed the formation of wormlike micelle structure. Moreover, it switched back to the original low-viscosity state by subsequent adding 1% aqueous solution of NaOH, then led to the breakdown of fracturing fluid. The thickening and breaking glue of the system are easy to carry out, sand-carrying ability is strong (1.64-1.8 cm/h), and temperature performance is very good (60 ℃). It is expected to be used in oilfield fracturing operation.