Experimental investigation of the effects of ultrasonic stimulation on adsorption, desorption and seepage characteristics of shale gas

Abstract

To verify the feasibility of applying ultrasonics to enhancing gas production from shale gas reservoirs, experimental study on the effects of ultrasonics on adsorption, desorption and seepage characteristics of shale gas using four samples from Sichuan Basin has been carried out. Adsorption and desorption of methane, were tested by volume method under different conditions, while the permeabilities of shale samples were tested by steady state method under different conditions. Results show that ultrasonics has a negative effect on the adsorption of shale gas, while a positive effect on desorption, resulting from the fact that ultrasonics treatment can enhance the vibration of gas molecules to break down the adsorption equilibrium. Further, the permeability dropped significantly with the effective confining pressure and pore pressure increasing, resulting from that high confining pressure decreases the area of seepage channels. The results also illustrate that permeability increases with the ultrasonics power increasing, presumbly by forming microfractures in shale which results in significant increase in the area of seepage channels.