Model Experiment on the Enhancement of Seismic Signal for Fracture Detection by Injecting Air Bubble

This paper presents the model experiment on the enhancement of seismic signals for fracture detection. To enhance seismic signals from fractures, we propose a repeated measurement and a differential analysis by changing the seismic properties of fractures actively. Air bubbles are injected in the fluid-filled fracture to change its seismic properties. We performed the bar model experiment and the block model experiment to investigate the effect of the injection of air bubbles on P-wave propagation. As the result, the amplitude of the transmitted P-wave is attenuated and that of the reflected P-wave is emphasized by injecting air bubbles in the fracture. The effect of air bubbles can be represented as the variation of the density, the velocity and the attenuation characteristics. We can estimate the area where air bubbles are distributed by monitoring the amplitude attenuation of the transmitted P-wave.