Seismic low-frequency anomalies in multiple reflections from thinly-layered poroelastic reservoirs
Published in
SEG/San Antonio 2007 Annual Meeting
Publication date
25 September 2007
Abstract
Seismic low-frequency (1-10 Hz) anomalies in multiple reflections can be related to hydrocarbon-saturated rocks with high values of attenuation. We study reflections in the low-frequency range from a poroelastic layered reservoir embedded in an elastic background medium, using Biot’s theory and 1D finite-difference modeling of wave propagation. In this model, the reservoir has a constant thickness and consists of a variable number of alternating pairs of fluid-saturated layers. For few layers (coarse layers), the reflections from the reservoir are identical when we compare results for poroelastic and equivalent elastic layers. For many layers (thin layers), the results are considerably different. When we choose, for example, the impedance of the background medium similar to the elastic Backus-averaged impedance of the reservoir, the reflections disappear in the elastic case, while in the poroelastic they become significant, due to velocity dispersion caused by wave-induced viscous fluid flow and attenuation between layers (interlayer-flow model).
