Effects of ultrasonic and surfactant coupling treatment on the wettability of coal

Abstract

Coal wettability has an important influence on the permeability of water-injected coal seam. The coal seam water injection effectively improves the ultrasonic excitation effect, and the surfactant can mitigate the water lock effect produced during water injection. To study the effect of ultrasonic and surfactant coupling treatment on the wettability of coal, the ultrasonic excitation fracturing system was used to perform excitation experiments on different coal samples. The coal microscopic properties were determined, and the coal wettability was characterized based on the contact angles. The experimental results demonstrate that the general decrease in the content of hydrophilic groups after the coal was coupled with ultrasonic and surfactant compared to the alkyl polyglycoside (APG) treatment, and the decrease in the content of oxygen-containing functional groups was more obvious; the pore size, pore volume and specific surface area (SSA) of coal all increased to different degrees, especially for pore size and pore volume; under the treatment of ultrasonic or surfactant, the coal wettability was enhanced, while the wettability was further enhanced by the coupling treatment; when ultrasonic was coupled with the surfactant, an advantageous complementary effect could be formed, which improved the final effect of the coupling treatment.