Effect of fracture fill on seismic attenuation and dispersion in fractured porous rocks

Kong, Liyun; Gurevich, Boris; Müller, Tobias M.; Wang, Yibo; Yang, Huizhu

doi:10.1093/gji/ggt354

Cited by 55 publications

(37 citation statements)

References 27 publications

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“…It then follows that if the effective isotropic background property is frequency dependent, then the effect on P-wave anisotropy would be frequency dependent. Dispersion as a result of wave-induced fluid flow is also known to be caused by the presence of fractures Gurevich et al 2009;Kong et al 2013). It can be seen that a larger fluid effect on anisotropy is observed when dispersion is considered as a result of wave-induced fluid flow from the fractured rock model (Fig.…”

Section: O D E L L I N G I N S I G H T a N D Discussion Smentioning

confidence: 94%

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

Amalokwu¹,

Chapman²,

Best³

et al. 2015

Geophys. J. Int.

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S U M M A R YThe 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 'ε' 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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Section: O D E L L I N G I N S I G H T a N D Discussion Smentioning

confidence: 94%

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

Amalokwu¹,

Chapman²,

Best³

et al. 2015

Geophys. J. Int.

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“…Although our modelling exercise only incorporates the squirt mechanism at full water saturation, using the simple modelling approach we adopted, it is straightforward to see that in the presence of squirt flow at partial liquid/gas saturation the fluid effect on the S2 wave would be even greater (increasing V s2 further), hence reducing the SWS. Dedicated partial saturation models could be introduced to make the modelling more rigorous in future (e.g., Kong et al, 2013).…”

Section: Insight From Modelling Study and Discussionmentioning

confidence: 99%

Experimental observation of water saturation effects on shear wave splitting in synthetic rock with fractures aligned at oblique angles

Amalokwu

Chapman

Best³

et al. 2014

Geophysical Journal International

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Contact NOC NORA team at publications@noc.soton.ac.ukThe NERC and NOC trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. SWS is commonly used for fractured rock characterisation and has been shown to be sensitive to fluid type. The presence of partial liquid/gas saturation is also known to affect the elastic properties of rocks. The combined effect of both fractures and partial liquid/gas saturation is still unknown. Using synthetic, silica-cemented sandstones with aligned pennyshaped voids, we conducted laboratory ultrasonic experiments to investigate the effect fractures aligned at an oblique angle to wave propagation would have on SWS under partial liquid/gas saturation conditions. The result for the fractured rock shows a saturation dependence which can be explained by combining a fractured rock model and a partial saturation model. At high to full water saturation values, shear wave splitting decreases as a result of the fluid bulk modulus effect on the quasi-shear wave. This bulk modulus effect is frequency dependent as a result of wave-induced fluid flow mechanisms, which would in turn lead to frequency dependent SWS. This result suggests the possible use of SWS for discriminating between full liquid saturation and partial liquid/gas saturation.3

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“…Instead of specifying the shapes of the background pores, the second type of models describe the background properties using the macroscopic parameters (such as porosity and permeability). This allows us to employ the Biot‐Gassmann theory to study the FB‐WIFF mechanism, for which quite a few models have been developed (e.g., Ba et al, , , ; Brajanovski et al, ; Fu et al, ; Galvin & Gurevich, ; Guo et al, , ; Gurevich et al, ; Kong et al, ). The effects of FB‐WIFF on the P ‐wave dispersion and attenuation are studied in detail using these models.…”

Section: Introductionmentioning

confidence: 99%

Effects of Coupling Between Wave‐Induced Fluid Flow and Elastic Scattering on P‐Wave Dispersion and Attenuation in Rocks With Aligned Fractures

Guo

Gurevich

2020

JGR Solid Earth

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Fracture‐background wave‐induced fluid flow (FB‐WIFF) and elastic scattering are considered two important mechanisms for P‐wave dispersion and attenuation in the fractured and porous fluid‐saturated rock. While numerous theoretical models have been proposed to study these two mechanisms, their coupling effects are seldom studied. Hence, in this work, we investigate the coupling between these two mechanisms theoretically based on the Biot equations of dynamic poroelasticity. The P wave is assumed to propagate perpendicular to the fracture plane in the fluid‐saturated porous rock with aligned penny‐shaped fractures. The general solutions are first obtained from the governing equations, then the expressions for the coefficients of the general solutions are derived using the boundary conditions. To illustrate the influencing factors on the coupling between FB‐WIFF and elastic scattering, a numerical example is given. The results show that the coupling strength between FB‐WIFF and elastic scattering are greatly influenced by the ratio of fluid viscosity to background permeability. With the decrease of this ratio, the coupling strength becomes stronger. Furthermore, the coupling effects are also affected by the fracture radius and thickness. However, the fracture density and fluid bulk modulus have negligible influence on the coupling effects. This new model shows good agreement with other theories. Furthermore, comparison of this new model with the linear superposition of FB‐WIFF and elastic scattering indicates the strong nonlinear coupling between these two mechanisms when their characteristic frequencies are close. Finally, the extension of this model and implications of our results for seismic exploration and sonic logging are discussed.

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Effect of fracture fill on seismic attenuation and dispersion in fractured porous rocks

Cited by 55 publications

References 27 publications

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

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

Experimental observation of water saturation effects on shear wave splitting in synthetic rock with fractures aligned at oblique angles

Effects of Coupling Between Wave‐Induced Fluid Flow and Elastic Scattering on P‐Wave Dispersion and Attenuation in Rocks With Aligned Fractures

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