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Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures

Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures
Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures
The seismic properties of rocks are known to be sensitive to partial liquid or gas saturation, and to aligned fractures. P-wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid. However, studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface. An understanding of the effects of partial liquid or gas saturation on P-wave anisotropy could help improve seismic characterization of fractured, gas bearing reservoirs. Using octagonal-shaped synthetic sandstone samples, one containing aligned penny-shaped fractures and the other without fractures, we examined the influence of water saturation on P-wave anisotropy in fractured rocks. In the fractured rock, the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures. Consequently, the anisotropy parameter ‘?’ decreases as a result of this fluid stiffening effect. These effects are frequency dependent as a result of wave-induced fluid flow mechanisms. Our observations can be explained by combining a frequency-dependent fractured rock model and a frequency-dependent partial saturation model.
Fracture and flow, Body waves, Seismic anisotropy, Acoustic properties
0956-540X
1088-1095
Amalokwu, Kelvin
a88bc1e5-5577-49a6-a503-fcd9ea12d8fe
Chapman, Mark
6f13eb72-ad0e-4c7a-b60c-92387a707cf4
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Minshull, Timothy A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Li, Xiang-Yang
b902023b-aa5b-477b-a97b-013173349ce1
Amalokwu, Kelvin
a88bc1e5-5577-49a6-a503-fcd9ea12d8fe
Chapman, Mark
6f13eb72-ad0e-4c7a-b60c-92387a707cf4
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Minshull, Timothy A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Li, Xiang-Yang
b902023b-aa5b-477b-a97b-013173349ce1

Amalokwu, Kelvin, Chapman, Mark, Best, Angus I., Minshull, Timothy A. and Li, Xiang-Yang (2015) Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures. Geophysical Journal International, 202 (2), 1088-1095.

Record type: Article

Abstract

The seismic properties of rocks are known to be sensitive to partial liquid or gas saturation, and to aligned fractures. P-wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid. However, studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface. An understanding of the effects of partial liquid or gas saturation on P-wave anisotropy could help improve seismic characterization of fractured, gas bearing reservoirs. Using octagonal-shaped synthetic sandstone samples, one containing aligned penny-shaped fractures and the other without fractures, we examined the influence of water saturation on P-wave anisotropy in fractured rocks. In the fractured rock, the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures. Consequently, the anisotropy parameter ‘?’ decreases as a result of this fluid stiffening effect. These effects are frequency dependent as a result of wave-induced fluid flow mechanisms. Our observations can be explained by combining a frequency-dependent fractured rock model and a frequency-dependent partial saturation model.

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Geophys. J. Int.-2015-Amalokwu-1088-95.pdf - Version of Record
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More information

Published date: August 2015
Keywords: Fracture and flow, Body waves, Seismic anisotropy, Acoustic properties
Organisations: Geology & Geophysics, Marine Geoscience

Identifiers

Local EPrints ID: 382526
URI: https://eprints.soton.ac.uk/id/eprint/382526
ISSN: 0956-540X
PURE UUID: 2af6017f-eb7e-4be3-b2e8-c7074f43dbcc
ORCID for Timothy A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 06 Oct 2015 14:06
Last modified: 06 Jun 2018 12:53

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