Macro-flow and Velocity Dispersion

Deformation resulting from a compressional wave can cause pore fluid motion on the order of the wavelength. If the fluid mobility is high, pressure can be equilibrated between regions of gas versus brine saturation. This can result in a relaxed, drained velocity even lower than dry or gas saturated velocities. This diffusion of fluid pressure can cause a gas-water contact that looks sharp at high (logging) frequencies to be gradational at seismic frequencies. This fluid motion can also result in high attenuation.