Synergistic effects of potassium alginate and silicates co-inhibition performance in shale hydration

High performance hydration inhibitors are recognized as an attractive solution to address wellbore instability associated with water-based drilling fluids. Nevertheless, conventional inhibitors still face a dilemma regarding the balance between inhibition performance and compatibility, including rheological and filtration properties. Herein, we proposed an organic-inorganic composite inhibitor that combines polymer adsorption and ion intercalation to provide synergistic inhibition properties. The results demonstrated that the composite inhibitors reduced the clay swelling rate from 50.7 to 22.4% and increased shale recovery from 71.4 to 90.2% compared with that in K2SiO3 solution, revealing the synergistic inhibition properties between ion exchange and film coating effect. In addition, the hydrogen bonding interaction between potassium alginate (PA) and clay particles effectively alleviates performance deterioration of base fluids containing K2SiO3, as evidenced by the apparent viscosity increased from 14.0 to 35.5 mPa·s, plastic viscosity increased from 4.0 to 25.0 mPa·s and filtration loss reduced from 35.2 to 20.4 mL after rolling at 120 °C. The intermolecular interaction between clay and PA facilitates the adsorption of polysaccharide chains onto clay surface, which was confirmed by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Moreover, X-ray diffraction (XRD), zeta potential and particle size distribution verified the suppression of electric double layers caused by K+ ions intercalation. This study validates the feasibility of organic-inorganic hybrid materials as shale hydration inhibitors, utilizing the synergistic effects of polymer adsorption and cation intercalation. Furthermore, the study highlights the great potential of combining PA with silicates to maintain wellbore stability.