TY - JOUR

T1 - Attenuation mechanisms in fractured fluid-saturated porous rocks

T2 - a numerical modelling study

AU - Caspari, Eva

AU - Novikov, Mikhail

AU - Lisitsa, Vadim

AU - Barbosa, Nicolás D.

AU - Quintal, Beatriz

AU - Rubino, J. Germán

AU - Holliger, Klaus

N1 - Publisher Copyright: © 2018 European Association of Geoscientists & Engineers

PY - 2019/5/1

Y1 - 2019/5/1

N2 - Seismic attenuation mechanisms receive increasing attention for the characterization of fractured formations because of their inherent sensitivity to the hydraulic and elastic properties of the probed media. Attenuation has been successfully inferred from seismic data in the past, but linking these estimates to intrinsic rock physical properties remains challenging. A reason for these difficulties in fluid-saturated fractured porous media is that several mechanisms can cause attenuation and may interfere with each other. These mechanisms notably comprise pressure diffusion phenomena and dynamic effects, such as scattering, as well as Biot's so-called intrinsic attenuation mechanism. Understanding the interplay between these mechanisms is therefore an essential step for estimating fracture properties from seismic measurements. In order to do this, we perform a comparative study involving wave propagation modelling in a transmission set-up based on Biot's low-frequency dynamic equations and numerical upscaling based on Biot's consolidation equations. The former captures all aforementioned attenuation mechanisms and their interference, whereas the latter only accounts for pressure diffusion phenomena. A comparison of the results from both methods therefore allows to distinguish between dynamic and pressure diffusion phenomena and to shed light on their interference. To this end, we consider a range of canonical models with randomly distributed vertical and/or horizontal fractures. We observe that scattering attenuation strongly interferes with pressure diffusion phenomena, since the latter affect the elastic contrasts between fractures and their embedding background. Our results also demonstrate that it is essential to account for amplitude reductions due to transmission losses to allow for an adequate estimation of the intrinsic attenuation of fractured media. The effects of Biot's intrinsic mechanism are rather small for the models considered in this study.

AB - Seismic attenuation mechanisms receive increasing attention for the characterization of fractured formations because of their inherent sensitivity to the hydraulic and elastic properties of the probed media. Attenuation has been successfully inferred from seismic data in the past, but linking these estimates to intrinsic rock physical properties remains challenging. A reason for these difficulties in fluid-saturated fractured porous media is that several mechanisms can cause attenuation and may interfere with each other. These mechanisms notably comprise pressure diffusion phenomena and dynamic effects, such as scattering, as well as Biot's so-called intrinsic attenuation mechanism. Understanding the interplay between these mechanisms is therefore an essential step for estimating fracture properties from seismic measurements. In order to do this, we perform a comparative study involving wave propagation modelling in a transmission set-up based on Biot's low-frequency dynamic equations and numerical upscaling based on Biot's consolidation equations. The former captures all aforementioned attenuation mechanisms and their interference, whereas the latter only accounts for pressure diffusion phenomena. A comparison of the results from both methods therefore allows to distinguish between dynamic and pressure diffusion phenomena and to shed light on their interference. To this end, we consider a range of canonical models with randomly distributed vertical and/or horizontal fractures. We observe that scattering attenuation strongly interferes with pressure diffusion phenomena, since the latter affect the elastic contrasts between fractures and their embedding background. Our results also demonstrate that it is essential to account for amplitude reductions due to transmission losses to allow for an adequate estimation of the intrinsic attenuation of fractured media. The effects of Biot's intrinsic mechanism are rather small for the models considered in this study.

KW - Attenuation

KW - Numerical study

KW - Rock Physics

KW - DISPERSION

KW - ANISOTROPY

KW - MODULI

KW - SEISMIC ATTENUATION

KW - CONNECTIVITY

KW - MEDIA

KW - DIFFUSION

KW - ACOUSTIC PROPAGATION

KW - SCATTERING ATTENUATION

KW - WAVE-PROPAGATION

UR - http://www.scopus.com/inward/record.url?scp=85052401369&partnerID=8YFLogxK

U2 - 10.1111/1365-2478.12667

DO - 10.1111/1365-2478.12667

M3 - Article

AN - SCOPUS:85052401369

VL - 67

SP - 935

EP - 955

JO - Geophysical Prospecting

JF - Geophysical Prospecting

SN - 0016-8025

IS - 4

ER -