Characterization of Seismic Anisotropy of the Marcellus Shale from - - PowerPoint PPT Presentation

Characterization of Seismic Anisotropy of the Marcellus Shale from Borehole Data

Sharif Morshed Ph.D. Aspirant

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Advisor : Dr. Robert Tatham

Talk Outline

• Seismic Anisotropy : Theoretical Basics
• Dipole Sonic Tool
• Anisotropy Characterization

The Marcellus Shale Data VTI Analysis Backus Average HTI Analysis Fracture Modeling

• Conclusion
• Future Work

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Isotropic Anisotropic

Seismic Anisotropy

Velocities are same in all directions Velocities are NOT same in all directions

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Simple Anisotropic System

Tatham & McCormack, 1991

VTI HTI

Transverse Isotropy Tensor

Voigt notation for VTI system

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Voigt notation for HTI system

Engelder, 2009 Milner, 2010

• Fractures
• Bedding parallel

cracks/ layering

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Anisotropy in the Marcellus Shale

Outcrop Thin Section and SEM image

Anisotropy Characterization

• Lab Measurement data
• Borehole Sonic data
• Surface Seismic data

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Velocities from Borehole Sonic Data

• Compressional and Shear slowness

Monopole Source (7-20kHz)--Vp(0o), Vs(0o)

• Shear Slowness Fast and Slow

Dipole Source (2-4kHz)—Vs1,Vs2

• Stoneley Slowness

Horizontal Shear wave slowness

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Dipole Sonic Tool

Shear Slowness Fast and Slow Dipole Source (2-4kHz)—Vs1,Vs2

• > Estimate of C44, C55

Zemanek et al, 1991 Brie et al, 1998

Anisotropy (ϒ)

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The Marcellus Shale

Middle Devonian marine organic shale extensive in New York, Pennsylvania, Ohio and West Virginia

• For VTI, Thomsen (1986) parameters
• C33=ρ(Vp(0o))2
• C44=C55=ρ(Vs(0o))2
• C66=ρ(Vs(90o))2
• C11=?, C13=?, Ɛ=?, δ=?

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Estimation of VTI Anisotropic parameter from Dipole log

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Thomsen (1986) ϒ from Monopole log

0.05 0.1 0.15 0.2 0.25 0.3 20 40 60 80 100 120 Thomsen Gamma Count

C44--Vertical monopole shear slowness C66--Horizontal shear slowness from stoneley slowness

VTI Anisotropy at Seismic Scale

• Upscaling

Seismic frequency--~order of 10’s, like 50 Hz

Borehole monopole frequency--~ 5-10kHz Borehole dipole frequency -- ~ 2 kHz

• Backus (1962) Average
• a. Upscaling at seismic wavelength
• b. Full VTI tensor
• c. Estimation of Ɛ, γ, and δ

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Thomsen parameters from Backus (1962)

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• 0.01
• 0.005

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 8340 8360 8380 8400 8420 8440 8460 8480 8500 8520

Thomsen (1986) Parameter Depth (ft)

Epsilon Gamma Delta

Upper Marcellus Lower Marcellus

Averaging Length= 20 ft

Ɛ ϒ δ Upper Marcellus 0.0052 0.0071

• 0.0012

Lower Marcellus 0.0029 0.0033

• 0.0001

Total Marcellus 0.0065 0.0086

• 0.0014

Upscaled Velocities using Backus (1962)

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HTI Anisotropy

Voigt notation for stiffness tensor of HTI system

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• C44=ρ(Vs2)2
• C66=C55=ρ(Vs1)2

Average Wave length ~ 3.5 ft

Fracture Modeling

Hudson (1982) for isolated penny shaped cracks, 𝑑𝑗𝑘

𝑓𝑔𝑔 = 𝑑𝑗𝑘 0 + 𝑑𝑗𝑘 1 + 𝑑𝑗𝑘 2

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0.01 0.02 0.03 0.04 0.05 0.06 2 4 6 8 10 12 14 Crack Induced Porosity Count

Aspect ratio : 0.07 - 0.15 Crack density : 0.005-0.09 First Order correction for dry cracks

Fracture Modeling Results

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Dry cracks are substituted with Gas, Using Gassmann (1951)

Conclusion

• The Marcellus shale is complex in terms
• f anisotropy.
• The Marcellus Shale is very weakly VTI at

seismic frequency.

• The Marcellus shale may be fractured.
• More complex model like Orthorhombic

consideration may give better result.

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Future Work

• AVOZ
• Orthorhombic model
• Orientation distribution function with Organic

porosity consideration

• Calibration and tie with core and surface seismic

data

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Acknowledgements

• EDGER Forum
• Dr. Robert H. Tatham
• Dr. Kyle Spikes

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Special Thanks to our Sponsors

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