Does Fluid Viscosity Influence Seismic Velocity?

N-20 DOES FLUID VISCOSITY INFLUENCE SEISMIC VELOCITY? MARK CHAPMAN 1 The introduction of the time-lapse methodology requires a clear understanding of how the seismic properties of rock respond to changing reservoir conditions. Perhaps the most fundamental such question is the fluid-substitution problem: the attempt to predict the seismic effect resulting from a change to the saturating fluid. Gassmann's theorem (Gassmann 1951) and its extensions (Brown and Korringa 1975) have traditionally formed the theoretical basis for attempts to solve the fluid-substitution problem in practice. The formal statement of Gassmann's result is: N sat ⎛ N ⎞ ⎜ ⎜1 − N ⎟