1887
  1. Home
  2. A-Z Publications
  3. Geophysical Prospecting
  4. Volume 64, Issue 4
  5. Article
Volume 64 Number 4
  • E-ISSN: 1365-2478

Abstract

ABSTRACT

A major cause of attenuation in fluid‐saturated media is the local fluid flow (or squirt flow) induced by a passing wave between pores of different shapes and sizes. Several squirt flow models have been derived for isotropic media. For anisotropic media, however, most of the existing squirt flow models only provide the low‐ and high‐frequency limits of the saturated elastic properties. We develop a new squirt flow model to account for the frequency dependence of elastic properties and thus gain some insight into velocity dispersion and attenuation in anisotropic media. In a companion paper, we focused on media containing aligned compliant pores embedded in an isotropic background matrix. In this paper, we investigate the case for which anisotropy results from the presence of cracks with an ellipsoidal distribution of orientations due to the application of anisotropic stress. The low‐ and high‐frequency limits of the predicted fluid‐saturated elastic properties are respectively consistent with Gassmann theory and Mukerji–Mavko squirt flow model. In the most important case of liquid saturation, analytical expressions are derived for elastic properties and Thomsen anisotropy parameters. The main observations drawn from this model are as follows. Crack closure perpendicular to the applied stress leads to an increase in seismic velocities as a function of stress in the direction of applied stress and a decrease in squirt‐flow‐induced dispersion and attenuation in this direction. The anisotropy of squirt flow dispersion engenders a decrease in the degree of anisotropy with frequency. The stress‐induced anisotropy remains elliptical, even in saturated media, for all frequency ranges.

© 2016 European Association of Geoscientists & Engineers © 2016 European Association of Geoscientists & Engineers
Loading

Article metrics loading...

/content/journals/10.1111/1365-2478.12385
2016-06-08
2024-04-18

  • From This Site

    /content/journals/10.1111/1365-2478.12385
    dcterms_title,dcterms_subject,pub_keyword
    -contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution
    10
    5
Loading full text...

Full text loading...

References

  1. AlkhalifahT. and TsvankinI.1995. Velocity analysis for transversely isotropic media. Geophysics60, 1550–1566.
     [Google Scholar]
  2. BrajanovskiM., GurevichB. and SchoenbergM.2005. A model for P‐wave attenuation and dispersion in a porous medium permeated by aligned fractures. Geophysical Journal International163, 372–384.
     [Google Scholar]
  3. ChapmanM.2009. Modeling the effect of multiple sets of mesoscale fractures in porous rock on frequency‐dependent anisotropy. Geophysics74, D97–D103.
     [Google Scholar]
  4. ChaudhryN.1995. Effects of aligned discontinuities on the elastic and transport properties of reservoir rocks. PhD thesis, Royal School of Mines, UK.
  5. ColletO. and GurevichB.2013. Fluid dependence of anisotropy parameters in weakly anisotropic porous media. Geophysics78, 1–9.
     [Google Scholar]
  6. ColletO., GurevichB., MadadiM. and PervukhinaM.2014. Modeling elastic anisotropy resulting from the application of triaxial stress. Geophysics79, C135–C145.
     [Google Scholar]
  7. GassmannF.1951. Über die Elastizität poröser Medien. Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich, 96, 1–23.
     [Google Scholar]
  8. GurevichB., MakarynskaD., de PaulaO.B. and PervukhinaM.2010. A simple model for squirt‐flow dispersion and attenuation in fluid‐saturated granular rocks. Geophysics75, N109–N120.
     [Google Scholar]
  9. GurevichB., MakarynskaD. and PervukhinaM.2009a. Are penny‐shaped cracks a good model for compliant porosity? Presented at the 2009 SEG Annual Meeting.
  10. GurevichB., MakarynskaD. and Pervukhina, M.2009b. Ultrasonic moduli for fluid‐saturated rocks: Mavko‐Jizba relations rederived and generalized. Geophysics74, N25–N30.
     [Google Scholar]
  11. GurevichB., PervukhinaM. and MakarynskaD.2011. An analytic model for the stress‐induced anisotropy of dry rocks. Geophysics76, WA125–WA133.
     [Google Scholar]
  12. MavkoG. and JizbaD.1991. Estimating grain‐scale fluid effects on velocity dispersion in rocks. Geophysics56, 1940–1949.
     [Google Scholar]
  13. MavkoG., MukerjiT. and GodfreyN.1995. Predicting stress‐induced velocity anisotropy in rocks. Geophysics60, 1081–1087.
     [Google Scholar]
  14. MavkoG. and NurA.1975. Melt squirt in the asthenosphere. Journal of Geophysical Research80, 1444–1448.
     [Google Scholar]
  15. MukerjiT. and MavkoG.1994. Pore fluid effects on seismic velocity in anisotropic rocks. Geophysics59, 233–244.
     [Google Scholar]
  16. MurphyW.F., WinklerK.W. and KleinbergR.L.1986. Acoustic relaxation in sedimentary rocks: Dependence on grain contacts and fluid saturation. Geophysics51, 757–766.
     [Google Scholar]
  17. NurA. and SimmonsG.1969. Stress‐induced velocity anisotropy in rock: An experimental study. Journal of Geophysical Research74, 6667–6674.
     [Google Scholar]
  18. RasolofosaonP.1998. Stress‐induced seismic anisotropy revisited. Revue de/Institut Français du Pétrole53, 679–692.
     [Google Scholar]
  19. SayersC.1988. Stress‐induced ultrasonic wave velocity anisotropy in fractured rock. Ultrasonics26, 311–317.
     [Google Scholar]
  20. SayersC. and KachanovM.1995. Microcrack‐induced elastic wave anisotropy of brittle rocks. Journal of Geophysical Research100, 4149–4156.
     [Google Scholar]
  21. SayersC.M.2006. Sensitivity of time‐lapse seismic to reservoir stress path. Geophysical Prospecting54, 369–380.
     [Google Scholar]
  22. ShapiroS.2003. Elastic piezosensitivity of porous and fractured rocks. Geophysics68, 482–486.
     [Google Scholar]
  23. SunH. and PrioulR.2010. Relating shear sonic anisotropy directions to stress in deviated wells. Geophysics75, D57–D67.
     [Google Scholar]
  24. ThanoonD., BachrachR., ZdravevaO. and ChenS.2015. Tilted orthorhombic model building with geomechanics: Theory and observations. Presented at the 77th EAGE Conference and Exhibition 2015.
  25. ThomsenL. 1986. Weak elastic anisotropy. Geophysics51, 1954–1966.
     [Google Scholar]
  26. ZatsepinS.V. and CrampinS.1997. Modelling the compliance of crustal rock—I. Response of shear‐wave splitting to differential stress. Geophysical Journal International129, 477–494.
     [Google Scholar]
  27. ZhuY. and TsvankinI.2006. Plane‐wave propagation in attenuative transversely isotropic media. Geophysics71, T17–T30.
     [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.1111/1365-2478.12385
Loading
Frequency dependence of anisotropy in fluid saturated rocks – Part II: Stress‐induced anisotropy case
Geophysical Prospecting 64, 1085 (2016); https://doi.org/10.1111/1365-2478.12385
/content/journals/10.1111/1365-2478.12385
/content/journals/10.1111/1365-2478.12385
Loading

Data & Media loading...

  • Article Type: Research Article
Keyword(s): Anisotropy; Attenuation; Rock physics

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error