Seismic Attenuation, Dispersion and Anisotropy in Porous Rocks: Mechanisms and Models

date November 3, 2014
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Monday, November 3, 2014 1:30 p.m. ARL Auditorium

Dr. Boris Gurevich
Curtin University and CSIRO
Perth, Australia
http://www.csiro.au

Understanding and modelling of attenuation of elastic waves in fluid-saturated rocks is important for a range of geophysical technologies that utilise seismic, acoustic or ultrasonic amplitudes. A major cause of elastic wave attenuation is viscous dissipation due to the flow of the pore fluid induced by the passing wave. Wave-induced fluid flow occurs as a passing wave creates local pressure gradients within the fluid phase and the resulting fluid flow is accompanied with internal friction until the pore pressure is equilibrated. The fluid flow can take place on various length scales: for example, from compliant fractures into the equant pores (so-called squirt flow), or between mesoscopic heterogeneities like fluid patches in partially saturated rocks. A common feature of these mechanisms is heterogeneity of the pore space. I will explore how this heterogeneity affects attenuation, dispersion and anisotropy of porous rocks. I give a brief outline of a consistent theoretical approach that gives quantitative estimates of these phenomena and discuss rigorous bounds for attenuation and dispersion, which represent an extension of Hashin-Shtrikman bounds to viscoelastic media.

Boris Gurevich has MSc from Moscow State University (1981) and PhD from Moscow Institute of Geosystems (1988). In 1990s he worked at a number of institutions in Russia, Germany, UK and Israel before joining Curtin University and CSIRO in Perth, Australia in 2001 as Professor of Petroleum Geophysics. From 2010 he has served as head of Curtin’s Department of Exploration Geophysics and Director of the Curtin Reservoir Geophysics Consortium. His research interests include rock physics, poroelasticity, diffraction imaging and time lapse seismic monitoring.