Seminar: Seismic attenuation, dispersion, and anisotropy in porous rocks: Mechanisms and Models

by Prof. Boris Gurevich, Professor, Exploration Geophysics, Curtin University; CSIRO

Thursday 15 August 2019, 11AM–12PM, ARRC Auditorium

ABSTRACT: Understanding and modeling 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, such as fractures, compliant grain contacts, or fluid patches. Using theoretical calculations and experimental data, we will explore how this heterogeneity affects attenuation, dispersion, and anisotropy of porous rocks. I will outline a consistent theoretical approach that quantifies these phenomena and discuss rigorous bounds for attenuation and dispersion.