Synergistic Permeability Enhancement Mechanism of Coal Seams Integrating Superwettable Acidification and Superaerophobic Desorption

To address the low methane extraction efficiency and poor adaptability of conventional permeability enhancement technologies in low-permeability, mineral-rich coal seams, this study proposes a novel synergistic permeability enhancement mechanism integrating superwettable acidification and superaerophobic desorption. Taking high-rank coal from the Wangzhuang Coal Mine of Lu’an Group, Shanxi Province as the research object, ethanol was introduced into the conventional acid-surfactant system to construct a tailored superwettable acid solution. Systematic experiments on dissolution-seepage-wettability-gas desorption were performed to test the dissolution rate, mineral composition, pore-fracture structure, wettability, and permeability of coal under different acid solution systems, aiming to reveal the synergistic permeability enhancement mechanism of acidification-gas desorption combination processes. The results show that: (1) the superwettable acid solution reduces the contact angle between the acid solution and coal samples from 152° to 0° (realizing superhydrophilic spreading), with a dissolution rate 3.98 times higher than that of the single-component acid solution; (2) it effectively dissolves carbonate minerals, significantly decreasing the contents of Ca, Mg, and other major mineral elements while increasing the relative contents of kaolinite and quartz, and generating abundant interconnected dissolution pores and fractures on the coal surface; (3) coal permeability increases by 2.5 times after acidification; and (4) the superwettable acid solution forms a liquid film on the coal surface, endowing it with superaerophobicity (bubble contact angle >150°) and slippery behavior (sliding angle <6°), which reduces methane bubble resistance and promotes rapid bubble detachment. The research results provide a certain theoretical basis for the application of acidification and permeability enhancement technology in the methane control of low-permeability, mineral-rich coal seams.