Effect of fracturing fluid on the desorption-diffusion property of coal

Aiming at preventing the fracturing fluid significantly affecting the desorption-diffusion property of CBM reservoirs through spontaneously imbibing into the coal matrix, methane desorption-diffusion experiments before and after fracturing fluid treatment was conducted on the coal samples from No.15 coal seam of Qinshui basin. Besides, the variations of surface property and pore structure were also analyzed by FTIR, low temperature N₂ adsorption and SEM methods. The results showed that after fracturing fluid treatment the methane desorption ratio dropped by 10.23% and the damage extent of diffusion coefficient was 16.67%; under the influence of fracturing fluid, the hydrophilicity was enhanced, the effect of liquid retention was aggravated, the pore connectivity became worse, the specific surface area increased and the average pore size decreased. These changes revealed radically the microscopic mechanisms of the effect of fracturing fluid on the desorption-diffusion property of CBM reservoir. Finally, the control methods based on nano-particle plugging and surfactant technology were also proposed to prevent the damage to desorption-diffusion property of CBM reservoirs.