Open AccessSEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION
Author(s) -
Joel Walls,
M T Taner,
Gary Mavko,
Jack Dvorkin
Publication year - 2002
Language(s) - English
Resource type - Reports
DOI - 10.2172/834452
Subject(s) - attenuation , elastic modulus , dispersion (optics) , porosity , bulk modulus , velocity dispersion , geology , seismic wave , mechanics , geotechnical engineering , mineralogy , materials science , physics , optics , composite material , seismology , quantum mechanics , galaxy
In fully-saturated rock and at ultrasonic frequencies, the microscopic squirt flow induced between the stiff and soft parts of the pore space by an elastic wave is responsible for velocity-frequency dispersion and attenuation. In the seismic frequency range, it is the macroscopic cross-flow between the stiffer and softer parts of the rock. We use the latter hypothesis to introduce simple approximate equations for velocity-frequency dispersion and attenuation in a fully water saturated reservoir. The equations are based on the assumption that in heterogeneous rock and at a very low frequency, the effective elastic modulus of the fully-saturated rock can be estimated by applying a fluid substitution procedure to the averaged (upscaled) dry frame whose effective porosity is the mean porosity and the effective elastic modulus is the Backus-average (geometric mean) of the individual dry-frame elastic moduli of parts of the rock. At a higher frequency, the effective elastic modulus of the saturated rock is the Backus-average of the individual fully-saturated-rock elastic moduli of parts of the rock. The difference between the effective elastic modulus calculated separately by these two methods determines the velocity-frequency dispersion. The corresponding attenuation is calculated from this dispersion by using (e.g.) the standard linear solid attenuation model