 # 3-D Fault Visualization with Fracture Swarms

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3-D Fault Visualization with Fracture Swarms
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 cross- plotting 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: 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
Example (1): Standard processing vs. High Frequency (Xfreq) and P-impedance from inversion

Example (2): Wire Line P-impedance vs
Example (2): Wire Line P-impedance vs. Poisson’s Ratio, Colored by Effective porosity Poisson's Ratio P-impedance

Wireline: Rockies Cross plot
Poisson's Ratio P-impedance Effective Porosity Log

SEISMIC: Crossplot of P-impedance vs
SEISMIC: Crossplot of P-impedance vs. Poissons ratio same zones as effective porosity on wireline Poisson's Ratio 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

High E and low  = Brittle Rock
Cross-plot of Young's Modulus (E) vs. Poisson's Ratio () to Determine “Brittle” Rock for Induced Fracturing in Shale Poisson's Ratio 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 cross- plotting 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 wave (velocity) anisotropy and S wave (AVO) anisotropy can be described as ellipse. P waves and S waves slow down across fractures Neither P or S waves “see” fractures Parallel.

Azimuthal changes in velocity and amplitude
Vertical Fractures, or matrix anisotropy Dipping reflector Fault displacement, Heterogeneity

Sort Gathers by Azimuth Prior to Migration
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 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: 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.