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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

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**Simultaneous inversion for Fractures, Shales and Porosity**

By Bob Parney Ph.D.,

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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.

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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

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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

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**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

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**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.

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**Example (1): Standard processing vs**

Example (1): Standard processing vs. High Frequency (Xfreq) and P-impedance from inversion

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**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

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**Wireline: Rockies Cross plot**

Poisson's Ratio P-impedance Effective Porosity Log

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**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

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**Inline Close up of Porosity**

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**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

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**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

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Inline of E · and Stack Poisson's Ratio Young's Modulus ·

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**Cross-plot of Ymodrho to Poir**

Stack Poisson's Ratio Young's Modulus ·

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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.

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**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

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**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.

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**Azimuthal changes in velocity and amplitude**

Vertical Fractures, or matrix anisotropy Dipping reflector Fault displacement, Heterogeneity

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**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

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**Fracture Workflow Sector by Azimuth PSTM Coherence Pre-stack Inversion**

(Angle Stack)

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**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...

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**Magnitude of Poisson's Ratio Anisotropy (Max-Min) over Coherence on all azimuth stack.**

Poisson's Ratio and Coherency

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**Magnitude of P-Impedance Anisotropy (Max-Min) over Coherence on all azimuth stack.**

P-impedance and Coherency

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**Magnitude of Shear Anisotropy vs. Full Coherence**

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**Magnitude of Shear Anisotropy vs. S1 Coherence**

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**Magnitude of Shear Anisotropy vs. S2 Coherence**

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**Magnitude of Shear Anisotropy vs. S3 Coherence**

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**Magnitude of Shear Anisotropy**

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**Sector 3 Azimuth High Res. Eigen**

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**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.

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