Seismic rock physics experiment and study on seismic wave attenuation characteristics based on miscible fluid assumption

The propagation of seismic waves through reservoir rocks generates fluid pressure gradients, inducing relative fluid flow between pores. This manifests as velocity dispersion and attenuation phenomena, thereby influencing seismic wave characteristics. However, traditional attenuation rock physics models that consider the effects of fluid flow assume that the fluids in the pores are immiscible, while in reality, dissolution and diffusion inevitably occur between fluids. This limitation results in inadequate characterization of pore fluid impacts, affecting the accuracy of seismic rock physics models. The Wave Induced Gas Exsolution and Dissolution (WIGED) mechanism effectively explains the attenuation caused by dissolution and diffusion in multiphase fluids. Currently, there remains a lack of targeted experimental observations on dissolution-diffusion effects induced by pressure gradients, which constrains the application of this attenuated rock physical model. This study focuses on measuring and analyzing seismic wave attenuation characteristics in rocks saturated with two-phase (gas-liquid) miscible fluids. By setting up a rock physics measurement apparatus, it was observed that bubbles deform with pressure perturbations (pressure disturbances caused by seismic waves). Theoretical model numerical calculations verified the effectiveness of the WIGED mechanism in describing attenuation within the seismic frequency bands. This seismic wave attenuation characteristic is closely related to factors such as reservoir temperature, pressure, fluid distribution, pore structure, and fracture. The characteristics of the attenuation curve can be effectively characterized based on the standard linear solid model.