Synergistic effects of cationic trimeric fracturing fluids on gas-coal wettability modulation and pore structure...

Coal seam water injection fracturing technology significantly reduces coal dust concentration through modification of coal seam properties, representing a critical approach for achieving safe and efficient coal mining. However, the synergistic mechanism between conventional fracturing fluids in wetting modulation and pore remodeling remains unclear, limiting further optimization of their performance. To address this, this paper innovatively synthesized a cationic trimeric surfactant (CSJT). It was blended with dodecyl trimethyl ammonium bromide (DTAB) and potassium chloride (KCl) to form a composite fracturing fluid, designed to synergistically enhance coal seam modification. Through experiments including contact angle measurement and low-temperature nitrogen adsorption, the effects of the composite fracturing fluid on the wettability and pore structure of gas coal were evaluated, revealing the synergistic mechanism. The results demonstrated a significant wettability-altering effect of this system, as evidenced by reductions in surface tension to 27.379 mN/m and contact angle to 19.8°, resulting in a hydrophilic transformation of the coal. Simultaneously, the system effectively increased the content of hydrophilic functional groups in the coal samples and enlarged the average pore size, indicating significant pore expansion. The simulation results indicated that the system significantly enhanced water diffusion on the coal surface, yielding a diffusion coefficient (D) of 17.98 × 10^-9 m²/s and an interfacial adsorption layer thickness of 58.38 Å, thereby elucidating the dynamic mechanism of wettability enhancement at the molecular level. This study provides innovative material design strategies for coal seam water injection fracturing technology, thereby contributing to effective dust control and green mining practices.