LAUSR

Seismic waves propagating through rocks saturated with multiple fluids can be attenuated by fluid pressure diffusion (FPD) because of the contrast in compressibility between the different fluid phases. The compression of the pore space by a seismic wave induces a pressure gradient and consequently pressure diffusion between the fluid phases of different compressibility. FPD is also referred to as patchy saturation or wave induced fluid flow (WIFF). Attenuation and the associated dispersion of seismic waves by FPD are sensitive to the saturation and spatial distribution of the fluids as well as the rocks permeability (Müller et al., 2010; Pride et al., 2004). These qualities make seismic methods particularly interesting for monitoring CO2 storage sites in order to characterize the extent of a plume and for probing how effectively a formation is trapping the CO2 (Caspari et al., 2011; Ivanova et al., 2012; Zhu et al., 2017). However, accurately relating the fluid distribution to the seismic properties of the formation remains challenging because systematic and accurate laboratory measurements of frequency dependent attenuation and dispersion are still rare.