Ultrasonic anisotropic P-wave attenuation of shales under elevated pressures
- Liwei Ou (Colorado School of Mines) | Manika Prasad (Colorado School of Mines)
- Document ID
- Society of Exploration Geophysicists
- 2016 SEG International Exposition and Annual Meeting, 16-21 October, Dallas, Texas
- Publication Date
- Document Type
- Conference Paper
- 2016. Society of Exploration Geophysicists
- Shale, Anisotropy, Attenuation, Acoustic
- 0 in the last 30 days
- 34 since 2007
- Show more detail
The mechanisms of ultrasonic attenuation in reservoir rock are known to be sensitive to multiple rock physical properties; this study focuses on ultrasonic experiments that measure the anisotropic attenuation in shales as function of hydrostatic confining pressure; four Eagleford and Bakken samples were measured using new experimental setup that allows measuring anisotropic acoustic properties of sample simultaneously with only one core plug. Our tests show that P-wave attenuation is sensitive to confining pressure, and attenuation anisotropy is stronger than velocity anisotropy, especially for more isotropic samples; the highly active change of attenuation with pressure supports the opinion that attenuation is a highly sensitive parameter to rock intrinsic properties. Moreover, attenuation as a function of pressure clearly suggests a two-phase attenuation mechanism exists in shale: high aspect ratio pores/microcracks closure and the related scattering attenuation on crack surfaces dominate attenuation behavior under low pressure, while at high pressure the main mechanism shifts to intrinsic attenuation caused by grain/crack friction and anelasiticity. The measured anisotropy data could be used for understanding the loss mechanisms responsible for seismic attenuation, and would benefit the development of theoretical attenuation rock physics models, as well as the interpretation of well logging and seismic surveys in shale reservoirs.
Presentation Date: Wednesday, October 19, 2016
Start Time: 10:20:00 AM
Presentation Type: ORAL
|File Size||1 MB||Number of Pages||6|
Batzle,M.,R.Hofmann,M.Prasad,G.Kumar,L.Duranti, andD.-h.Han,2005,Seismic attenuation: Observations and mechanisms:75th Annual International Meeting, SEG, Expanded Abstracts,1565-1568,10.1190/1.2147991.
Best,A. I., andC.McCann,1995,Seismic attenuation and pore-fluid viscosity in clay-rich reservoir sandstones:Geophysics,60,1386–1397,10.1190/1.1443874.
Carcione,J. M.,J. E.Santos, andS.Picotti,2012,Fracture-induced anisotropic attenuation:Rock Mechanics and Rock Engineering,45,929–942,10.1007/s00603-012-0237-y.
Deng,J.,S.Wang, andD.-h.Han,2009,The velocity and attenuation anisotropy of shale at ultrasonic frequency:Journal of Geophysics and Engineering,6,269,10.1088/1742-2132/6/3/006.
Hornby,B. E.,1998,Experimental laboratory determination of the dynamic elastic properties of wet, drained shales:Journal of Geophysics Research: Solid Earth,103,29945–29964,10.1029/97JB02380.
Johnston,D. H., andM. N.Toksöz,1980,Ultrasonic P and S wave attenuation in dry and saturated rocks under pressure:Journal of Geophysical Research:Solid Earth,85,925–936,10.1029/JB085iB02p00925.
Klimentos,T., andC.McCann,1990,Relationships among compressional wave attenuation, porosity, clay content, and permeability in sandstones:Geophysics,55,998–1014,10.1190/1.1442928.
Lucet,N., andB.Zinszner,1992,Effects of heterogeneities and anisotropy on sonic and ultrasonic attenuation in rocks:Geophysics,57,1018–1026,10.1190/1.1443313.
Prasad,M., andM. H.Manghnani,1997,Effects of pore and differential pressure on compressional wave velocity and quality factor in Berea and Michigan sandstones:Geophysics,62,1163–1176,10.1190/1.1444217.
Prasad,M., andA.Nur,2003,Velocity and attenuation anisotropy in reservoir rocks:73rd Annual International Meeting, SEG, Expanded Abstracts,1652–1655,10.1190/1.1817621.
Rasolofosaon,P. N., andB. E.Zinszner,2002,Comparison between permeability anisotropy and elasticity anisotropy of reservoir rocks:Geophysics,67,230–240,10.1190/1.1451647.
Toksöz,M.,D.Johnston, andA.Timur,1979,Attenuation of seismic waves in dry and saturated rocks: I. Laboratory measurements:Geophysics,44,681–690,10.1190/1.1440969.
Vernik,L., andX.Liu,1997,Velocity anisotropy in shales: A petrophysical study:Geophysics,62,521–532,10.1190/1.1444162.
Woodruff,W. F.,A.Revil, andC.Torres-Verdín,2014,Laboratory determination of the complex conductivity tensor of unconventional anisotropic shales:Geophysics,79, no.5,E183–E200,10.1190/geo2013-0367.1.