Low-frequency anomalies of seismic-wave reflections from poroelastic layers
Published in
10th International Congress of the Brazilian Geophysical Society
Date of publication
19 November 2007
Abstract
Low-frequency (1-10 Hz) reflection anomalies can be related to hydrocarbon-saturated rocks with anomalous high values of attenuation. We study low frequency reflections from a poroelastic layered reservoir, which is embedded in an elastic background medium, using Biot’s theory and 1D finite-difference modeling of wave propagation. The reservoir has a constant thickness and consists of a variable number of two different alternating fluid saturated layers. For few layers the reflections from the reservoir are identical when we compare results for poroelastic layers with results for equivalent elastic layers. For many layers, i.e. thinly-layered reservoir, the results are considerably different. In the elastic case, the reflections disappear, because we have chosen the impedance of the background medium similar to the Backus-averaged (no-flow limit) impedance of the reservoir. In the poroelastic case, we observe considerable reflections, caused by velocity dispersion as a result of wave-induced viscous fluid flow and attenuation between layers.
