Abstract: To further investigate the factors influencing the physico-mechanical properties of organic-rich shale,experiments were conducted on Lower Silurian Longmaxi Formation shale from Changning Area of Sichuan Basin using an ultrasonic excitation system,a multi-frequency acoustic testing system,and a high-temperature high-pressure triaxial rheometer.The effects of ultrasonic excitation duration,power and frequency on the shale petrophysical and mechanical characteristics were analyzed,focusing on changes in shale porosity-permeability,P-wave velocity,attenuation coefficient,compressive strength,elastic modulus and Poisson's ratio.The experimental results show that shale porosity,permeability and P-wave attenuation coefficient increase with longer excitation time or higher ultrasonic excitation power;whereas shale P-wave velocity,compressive strength,and elastic modulus decrease with increasing ultrasonic excitation time and power,and Poisson's ratio increases slightly.With other factors constant,different ultrasonic excitation frequencies influence shale physico-mechanical properties,but the degree of influence is relatively insignificant.This study provides reference for validating the feasibility of ultrasonic stimulation for shale gas exploitation and for shale gas engineering applications.

Key words: shale, ultrasonic excitation, acoustic characteristics, mechanical characteristics