## Seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks

### Détails

ID Serval

serval:BIB_5A324F6F4F58

Type

**Article**: article d'un périodique ou d'un magazine.

Collection

Publications

Fonds

Titre

Seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks

Périodique

Geophysical Journal International

ISSN-L

0956-540X

Statut éditorial

Publié

Date de publication

2012

Peer-reviewed

Oui

Volume

188

Pages

1088 - 1102

Langue

anglais

Notes

Rubino2012

Résumé

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.

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.

Création de la notice

25/11/2013 17:31

Dernière modification de la notice

18/11/2016 13:39