The Effect of the Polyoxyethylene Ether Group on the Adsorption Capacity of the Adsorption Acidification Retarding...

Acidification is an important procedure to remove the plug and retard the acid-rock reaction to make acid reach deeper formations, which is beneficial for reservoir stimulation. The adsorption-type acidification retarding agent could form an adsorption film on the rock surface to isolate H⁺, resulting in a lower rate of the acid-rock reaction. In this study, the retarding agent AD-2 was synthesized by free radical polymerization using acrylamide (AM), octadecyl dimethyl allyl ammonium chloride (DMAAC-18), and allyloxypolyethylene glycol (APEG-2400) as raw materials, while AD-1 was synthesized from AM and DMAAC-18. The results of the Fourier transform infrared (FT-IR) spectrum and ¹H nuclear magnetic resonance (¹H NMR) indicated that the two retarding agents were successfully prepared. The adsorption behavior of AD-1 and AD-2 on the carbonate rock surface matched the Freundlich model and the adsorption capacity of AD-2 was about 3 times that of AD-1 at 70 °C and 9000 mg/L. Meanwhile, the higher the temperature, the greater the adsorption capacity of AD-2, but it was the opposite for AD-1. Furthermore, the introduction of the polyoxyethylene ether group was conducive to enhancing adhesion force and forming a dense adsorption film on the carbonate rock surface, which was evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The retarding rate of AD-2 and AD-1 was 90.1% and 78.3%, respectively, because the retarding agent AD-2 containing polyoxyethylene ether formed a much denser adsorption film on the rock surface. In addition, the viscosity of 9000 mg/L AD-2 retarding acid solution was as low as 12 mPa·s, compared with that of AD-1 retarding acid solution (42 mPa·s). This research could provide a reference for the design of an adsorption acidification retarding agent with low viscosity in reservoir stimulation.