Temperature-Responsive Hydrogel Carrier for Reducing Adsorption Loss of Petroleum Sulfonates.

Abstract

As an effective anionic surfactant for chemical flooding, petroleum sulfonate (PS) is often used in conjunction with alkalis to reduce the adsorption loss of PS onto rock and clay surfaces. However, alkali injection can lead to scaling, aggravate the water-sensitive effect of clays, and accelerate polymer hydrolysis. Here, a temperature-responsive biohydrogel-based carrier (XLK) was designed to protect PS from adsorption onto geological features. XLK, an aqueous mixture containing 0.5% xanthan gum, 0.5% locust bean gum, and 2% KCl, was a gel at room temperature and transformed gradually into a sol above 50 °C (sol/gel transition temperature, Tsol/gel). Below the Tsol/gel, most PS was retained in the gel, preventing the adsorption of PS onto quartz sand. Above the Tsol/gel, PS was released into the surrounding medium. After it had been loaded with PS, the storage modulus (G', Pa) of XLK increased from 102 to 103 and the loss modulus (G″, Pa) increased from 101 to 102. Environmental scanning electron microscopy micrographs showed that PS filled gaps within the cross-linked network structure of XLK. Compared with the aqueous XLK formulation, the addition of hydrolyzed polyacrylamide (HPAM) decreased the melt rate of XLK and the interfacial tension (IFT) of PS. Among the constituents of XLK loaded with PS, KCl had the most obvious effect of lowering the shear modulus of HPAM. Sufficient amounts of KCl were effective in reducing the IFT of PS to ultralow levels (10-3 mN/m).