Study of intrinsic versus scattering attenuation of seismic waves from borehole measurements

Abstract

© 2018 SEG. Estimation of scattering and intrinsic attenuation factors from seismic observations is of interest for subsurface imaging and characterization. We discuss a waveform inversion (WI) method for zero-offset seismic borehole data that explicitly models interference and multiple scattering in layered media using well logs. On the synthetic example, we show capability of WI to discriminate between scattering and intrinsic Q in 1D vertically inhomogeneous media. Depending on the scale of the supplied logs, the inverted Q-factors correspond either to the 'effective' attenuation or solely to the intrinsic absorption in rocks. We apply the WI to the nearly zero-offset VSP dataset acquired in the Nephrite-8 well (Cooper Basin, Australia). The borehole intersects the Patchawarra formation characterized by high-contrast interlayering of coal seams. For this formation, estimated intrinsic attenuation 1/Qint ˜ 0.014 is negligible compared to the stratigraphic filtering 1/Qscat ˜ 0.121±0.02. These 1/Qscat estimates are somewhat higher than those obtained by the application of the generalized O'Doherty - Anstey theory.