Numerical analysis of cleat effects on ultrasonic wave propagation in coal

Laboratory experiments investigated that ultrasonic wave stimulation can effectively enhance permeability of coal and improve production of unconventional reservoirs in field. The basic mechanism of coal-cleat effects on ultrasonic wave stimulation induced mechanical vibration in coal is poorly understood. In this paper, CT scan slices of coal sample are applied to conduct real numerical coal model to investigate effects of different physical attributes of materials in coal on ultrasonic wave propagation. Numerical simulation results reveal that cleats filled with minerals of higher velocity and density contribute to losing mechanical-vibration, but cleats filled with water or gas can trap the mechanical vibration at the interfaces of cleats. With the accumulation of mechanical vibration at interfaces of cleats, the permeability of coal will be enhanced.