+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks

Seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks

Geophysical Journal International 188(3): 1088-1102

Using a numerical approach, we explore wave-induced fluid flow effects in partially saturated porous rocks in which the gas water saturation patterns are governed by mesoscopic heterogeneities associated with the dry frame properties. The link between the dry frame properties and the gas saturation is defined by the assumption of capillary pressure equilibrium, which in the presence of heterogeneity implies that neighbouring regions can exhibit different levels of saturation. To determine the equivalent attenuation and phase velocity of the synthetic rock samples considered in this study, we apply a numerical upscaling procedure, which permits to take into account mesoscopic heterogeneities associated with the dry frame properties as well as spatially continuous variations of the pore fluid properties. The multiscale nature of the fluid saturation is taken into account by locally computing the physical properties of an effective fluid, which are then used for the larger-scale simulations. We consider two sets of numerical experiments to analyse such effects in heterogeneous partially saturated porous media, where the saturation field is determined by variations in porosity and clay content, respectively. In both cases we also evaluate the seismic responses of corresponding binary, patchy-type saturation patterns. Our results indicate that significant attenuation and modest velocity dispersion effects take place in this kind of media for both binary patchy-type and spatially continuous gas saturation patterns and in particular in the presence of relatively small amounts of gas. The numerical experiments also show that the nature of the gas distribution patterns is a critical parameter controlling the seismic responses of these environments, since attenuation and velocity dispersion effects are much more significant and occur over a broader saturation range for binary patchy-type gas water distributions. This analysis therefore suggests that the physical mechanisms governing partial saturation should be accounted for when analysing seismic data in a poroelastic framework. In this context, heterogeneities associated with the dry frame properties, which do not play important roles in wave-induced fluid flow processes per se, should be taken into account since they may determine the kind of gas distribution pattern taking place in the porous rock.

Please choose payment method:

(PDF emailed within 0-6 h: $19.90)

Accession: 036292523

Download citation: RISBibTeXText

DOI: 10.1111/j.1365-246x.2011.05291.x

Related references

Phase velocity dispersion and attenuation of seismic waves due to trapped fluids in residual saturated porous media. Vadose Zone Journal 11.3, 2012

Seismic dispersion and attenuation in saturated porous rocks with aligned fractures of finite thickness: Theory and numerical simulations Part 2: Frequency-dependent anisotropy. Geophysics 83(1): Wa63-Wa71, 2018

Low-frequency dispersion and attenuation in partially saturated rocks. Journal of the Acoustical Society of America 94(1): 359-0, 1993

Velocity and attenuation in partially saturated rocks; poroelastic numerical experiments. Geophysical Prospecting 51(6): 551-566, 2003

Wave attenuation in partially saturated porous rocks New observations and interpretations across scales. Leading Edge 33(6): 606-614, 2014

Estimating the dispersion of seismic P and S waves in partially saturated rocks. Eos, Transactions, American Geophysical Union 71(43): 1639, 1990

Attenuation at low seismic frequencies in partially saturated rocks Measurements and description of a new apparatus. Journal of Applied Geophysics 86(none), 2012

Seismic attenuation in partially saturated rocks: Recent advances and future directions. Leading Edge 33(6): 640-646, 2014

Comparative review of theoretical models for elastic wave attenuation and dispersion in partially saturated rocks. Soil Dynamics and Earthquake Engineering 26(6-7): 548-565, 2006

Modulus defect, velocity dispersion and attenuation in partially-saturated reservoirs of Jurassic sandstone, Indus Basin, Pakistan. Studia Geophysica et Geodaetica 60(1): 112-129, 2016

The relation between seismic P- and S-wave velocity dispersion in saturated rocks. Geophysics 59(1): 87-92, 1994

The relation between seismic P and S wave velocity dispersion in saturated rocks. Geophysics 59(1): 87-92, 1994

Modeling attenuation and dispersion in porous heterogeneous rocks with dynamic fluid modulus. Geophysics 80(3): D183-D194, 2015

Numerical Analysis of Velocity Dispersion in Multi-Phase Fluid-Saturated Porous Rocks. Pure and Applied Geophysics 174(3): 1219-1235, 2017

Some aspects of attenuation and dispersion of electromagnetic waves in fluid-saturated porous rocks and applications to dielectric constant well logging. Geophysics 47(3): 388-394, 1982