Synergistic Inhibition Effect of Organic Salt and Polyamine on Water-Sensitive Shale Swelling and Dispersion

Drilling fluid with strong inhibition performance is crucial in drilling water-sensitive shale formations. An organic salt compound and polyamine were tested for their ability to inhibit shale swelling and dispersion, both individually and in combination. The linear shale swelling rate can be suppressed to less than 20% when the inhibitors are combined, and the hot rolling recovery rate of shale cuttings can improve up to 85%. The interlamellar spacing d₀₀₁, zeta potential, particle size distribution, water activity, and adsorptive capacity of clays were tested to determine the suppression mechanism of the shale inhibitors. These results show that the organic salt YJS-2 functioned remarkably in crystal lattice fixation, electric double-layer compression, adjustment of water activity, and enhancement of polymer adsorption onto the clay particle surface. Polyamine can enter the clay mineral interlayer and compress the electric double-layer to some extent. It can also synergistically function with YJS-2. Therefore, a combination of these two shale inhibitors worked synergistically to provide crystal lattice fixation, electric double-layer compression, water activity adjustment, adsorption on the surface of clay particles, and encapsulation.