Report

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.