The Rock Physics Of Seismic Fluid Attributes

The tendency for a rock to change its bulk properties<br>upon fluid substitution is its "Fluid Sensitivity", and<br>is an intrinsic property of the rock. The magnitude of<br>the change in bulk rock properties is predictably<br>related to changes in seismic reflection attributes.<br>These changes are often called the "fluid effect". We<br>can speak of a fluid effect in relation to the classic<br>"A", "B", and "C" coefficients of the Aki & Richards<br>linearization. Fluid sensitivity and fluid effect are<br>often qualitatively related to porosity and P-wave<br>velocity, but can be more precisely related to an<br>important property of porous rocks called the "Biot<br>Coefficient". For most seismic attributes, the fluid<br>effect is independent of the surrounding lithology.<br>Only the fluid effect for the "B" attribute has a<br>component that depends on surrounding rocks. The<br>fluid effect for seismic attributes are separable in<br>relation to properties of the rock, and properties of<br>the fluid, and can be expressed as the product of rock<br>properties and fluid properties.