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 Advisor : Dr. Robert Tatham 1

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 2

Seismic Anisotropy Anisotropic Isotropic Velocities are same in all Velocities are NOT same in all directions directions 3

Simple Anisotropic System VTI HTI Tatham & McCormack, 1991 4

Transverse Isotropy Tensor Voigt notation for VTI system Voigt notation for HTI system 5

Anisotropy in the Marcellus Shale Outcrop Fractures • Bedding parallel • cracks/ layering Thin Section and SEM image Engelder, 2009 6 Milner, 2010

Anisotropy Characterization  Lab Measurement data  Borehole Sonic data  Surface Seismic data 7

Velocities from Borehole Sonic Data  Compressional and Shear slowness Monopole Source (7-20kHz)--Vp(0 o ), Vs(0 o )  Shear Slowness Fast and Slow Dipole Source (2-4kHz) — Vs 1 ,Vs 2  Stoneley Slowness Horizontal Shear wave slowness 8

Dipole Sonic Tool Shear Slowness Fast and Slow Dipole Source (2-4kHz) — Vs 1 ,Vs 2 -> Estimate of C 44 , C 55 9 Brie et al, 1998 Zemanek et al, 1991

The Marcellus Shale Middle Devonian marine organic shale extensive in New York, Pennsylvania, Ohio and West Virginia 10 Anisotropy (ϒ)

Estimation of VTI Anisotropic parameter from Dipole log • For VTI, Thomsen (1986) parameters  C 33 =ρ( Vp(0 o )) 2  C 44 =C 55 =ρ( Vs(0 o )) 2  C 66 =ρ( Vs(90 o )) 2  C 11 =?, C 13 =?, Ɛ =?, δ =? 11

Thomsen (1986) ϒ from Monopole log 120 100 C44--Vertical 80 monopole shear slowness Count 60 C66--Horizontal 40 shear slowness 20 from stoneley slowness 0 0 0.05 0.1 0.15 0.2 0.25 0.3 Thomsen Gamma 12

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 13

Thomsen parameters from Backus (1962) 8340 8360 Epsilon Gamma Delta 8380 Upper Marcellus 8400 Averaging 8420 Depth (ft) Length= 20 ft 8440 8460 Lower 8480 Marcellus 8500 8520 -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 Thomsen (1986) Parameter Ɛ ϒ δ Upper Marcellus 0.0052 0.0071 -0.0012 Lower Marcellus 0.0029 0.0033 -0.0001 14 Total Marcellus 0.0065 0.0086 -0.0014

Upscaled Velocities using Backus (1962) 15

HTI Anisotropy Voigt notation for stiffness tensor of HTI system C 44 =ρ(Vs 2 ) 2  C 66 =C 55 =ρ(Vs 1 ) 2  Average Wave length ~ 3.5 ft 16

Fracture Modeling Hudson (1982) for isolated penny shaped cracks, 𝑓𝑔𝑔 = 𝑑 𝑗𝑘 2 0 + 𝑑 𝑗𝑘 1 + 𝑑 𝑗𝑘 𝑑 𝑗𝑘 14 Aspect ratio : 0.07 - 0.15 12 Crack density : 0.005-0.09 10 8 First Order correction for Count dry cracks 6 4 2 0 0 0.01 0.02 0.03 0.04 0.05 0.06 Crack Induced Porosity 17

Fracture Modeling Results Dry cracks are substituted with Gas, Using Gassmann (1951) 18

Conclusion • The Marcellus shale is complex in terms of 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. 19

Future Work  AVOZ  Orthorhombic model  Orientation distribution function with Organic porosity consideration  Calibration and tie with core and surface seismic data 20

Acknowledgements  EDGER Forum  Dr. Robert H. Tatham  Dr. Kyle Spikes 21

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