Dispersive thoughts on shale

Several dispersion mechanisms are at play in clay rich shales. Most laboratory measurements show dispersion at low frequencies, and usually more dispersion from seismic to ultrasonic frequencies. Low frequency measurements on pure clay demonstrate that dispersion in clays may not rely on cracks. Bound water near mineral surfaces has largely enhanced viscosity and non-zero shear modulus and seems to contribute to dispersion in the seismic frequency range.