Tricon_INV_shales - Tricon Geophysics, Inc.

```Multi Azimuth
PSTM
High Resolution Coherence
Petrophysical Analysis,
Shear-log modeling
Multi-Azimuth, Simultaneous
Pre-stack Inversion
Porosity Cross-plotting
Multi Attribute
Visualization
3-D Fault Visualization with Fracture Swarms
Simultaneous inversion
for Fractures, Shales and Porosity
By Bob Parney Ph.D.,
Inversion
• We can use Inversion to calculate Elastic Coefficients:
Young's Modulus, Poisson's Ratio …
• In shales we can locate Brittle/Frac-able rock by crossplotting Young’s Modulus and Poisson’s Ratio.
• We can go a step further and map Elastic coefficients by
azimuth.
Inversion
1
2
3
Offset
• Reflection amplitude is controlled by Vp, Vs,  (density), incident angle
• Top of Layer 2: Difference between layer 1 and layer 2
• Bottom of Layer 2: Difference between layer 2 and layer 3
Inversion does the “accounting” to find Vp, Vs,  within reservoir
Post-stack inversion works by making a connection between
impedance contrast, the wavelet, and the final seismic section
P-impedance
Changes in P-imp
Wavelet
Stack
Pre-stack inversion: Using gathers or angle stacks we invert
For multiple offsets instead of just the stack
Gather/Angle Stack
P-wave Impedance
S-wave Impedance
Examples of Simultaneous Inversion:
Outputs:
(1) P-impedance (velocity*density)
(2) S-impedance
(3) Density (less reliable)
Can be used for:
1.
2.
3.
4.
5.
P-impedance/ Sonic Velocity for Lithology
Poissons ratio for Porosity and Vshale
Youngs Modulus: Identify frac zones
Interval Velocity for Pore-pressure
Azimuthal Inversion: Natural fractures and frac zones
by azimuth.
Example (1): Standard processing vs. High Frequency (Xfreq)
and P-impedance from inversion
Poisson's Ratio
Example (2): Wire Line P-impedance vs.
Poisson’s Ratio, Colored by Effective porosity
P-impedance
Poisson's Ratio
Wireline: Rockies Cross plot
P-impedance
Effective Porosity Log
Poisson's Ratio
SEISMIC: Crossplot of P-impedance vs.
Poissons ratio same zones as effective
porosity on wireline
P-impedance
Inline Close up of Porosity
Example (3) Shales: Elastic Moduli can be
calculated from Inversion results
Poissons ratio
 = F (Vp/Vs) = F (Pimp/Simp)
Youngs Modulus E ·  = 2 · (1+ ) · Simp2
(1) Either Cross plot E ·  (density) vs Poisson,
or (2) take  from the inversion and divide to get E
Poisson's Ratio
Cross-plot of Young's Modulus (E) vs. Poisson's Ratio () to
Determine “Brittle” Rock for Induced Fracturing in Shale
Young's Modulus
High E and low  = Brittle Rock
Inline of E · and 
Stack
Poisson's Ratio
Young's Modulus ·
Cross-plot of Ymodrho to Poir
Stack
Poisson's Ratio
Young's Modulus ·
Inversion
• We can use Inversion to calculate Elastic Coefficients:
Young's Modulus, Poisson's Ratio …
• In shales we can locate Brittle/Frac-able rock by crossplotting Young’s Modulus and Poisson’s Ratio.
• We can go a step further and map Elastic coefficients by
azimuth.
Example (4) Fractured Reservoir Analysis
from Seismic
• Migrate by sector to reduce uncertainty in source of
Anisotropy
• Simultaneous Inversion by Sector
• Stack then Coherence by Sector
• Now have all elastic moduli by azimuth
Map view of single set of vertical fractures
P waves and S waves slow
down across fractures
P wave (velocity) anisotropy and
S wave (AVO) anisotropy can be
described as ellipse.
Neither P or S waves “see” fractures
Parallel.
Azimuthal changes in velocity and amplitude
Vertical Fractures,
or matrix anisotropy
Dipping reflector
Fault displacement,
Heterogeneity
Pre-stack Migration by Azimuth for correct
azimuthal amplitudes and velocities
Sort Gathers by Azimuth Prior to Migration
N
Fracture Workflow
Sector by Azimuth
PSTM
Coherence
(Stack)
Pre-stack Inversion
(Angle Stack)
Fit Ellipses To Sectored Inversions
+



+
=
(1) Orientation of Maximum P and S Anisotropy
(2) Magnitude (Max-Min) of Maximum P and S
Anisotropy
(3) Magnitude and Orientation of Anisotropy in all
other Inversion Products: Poisson's Ratio, Young's
Modulus, Lambda Rho, Mu Rho...
Magnitude of Poisson's Ratio Anisotropy (Max-Min) over Coherence
on all azimuth stack.
Poisson's Ratio and Coherency
Magnitude of P-Impedance Anisotropy (Max-Min) over Coherence
on all azimuth stack.
P-impedance and Coherency
Magnitude of Shear Anisotropy vs. Full Coherence
Magnitude of Shear Anisotropy vs. S1 Coherence
Magnitude of Shear Anisotropy vs. S2 Coherence
Magnitude of Shear Anisotropy vs. S3 Coherence
Magnitude of Shear Anisotropy
Sector 3 Azimuth High Res. Eigen
Summary of Simultaneous Inversion:
Outputs:
(1) P-impedance (velocity*density)
(2) S-impedance
(3) Density (less reliable)
Can be used for:
1.
2.
3.
4.
5.
P-impedance/ Sonic Velocity for Lithology
Poisson's ratio for Porosity and Vshale
Young's Modulus: Identify frac zones
Interval Velocity for Pore-pressure
Azimuthal Inversion: Natural fractures and frac zones
by azimuth.
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