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Amit Suman and Tapan Mukerji 25 th SCRF Annual Meeting May 9 – 11, 2012

Sensitivity Analysis of Rock Physics Parameters for Modeling Time-Lapse Seismic(4D) response of Norne Field. Amit Suman and Tapan Mukerji 25 th SCRF Annual Meeting May 9 – 11, 2012. Joint Inversion Loop. Predicted flow and seismic response. Observed flow and seismic response. Model.

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Amit Suman and Tapan Mukerji 25 th SCRF Annual Meeting May 9 – 11, 2012

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  1. Sensitivity Analysis of Rock Physics Parameters for Modeling Time-Lapse Seismic(4D) response of Norne Field Amit Suman and Tapan Mukerji 25th SCRF Annual Meeting May 9 – 11, 2012

  2. Joint Inversion Loop Predicted flow and seismic response Observed flow and seismic response Model Reservoir SCRF

  3. Motivation Production data at time t Dynamic modeling Δ Pressure Δ Saturation Optimize mismatch Velocity at time t Rock physics modeling Seismic data at time t Update parameters

  4. Previous Work • Last year we investigated parameter sensitivity for modeling time-lapse seismic and flow data of Norne field • One of the investigated parameters was rock physics model • We didn’t investigate sensitivity of varying rock physics parameters on modeling 4D response SCRF

  5. Questions? “Should we investigate sensitive rock physics parameters in modeling 4D response?” “What are the sensitive rock physics parameters in modeling 4D response?” SCRF

  6. Norne Field Segment E F1H E3H In this study well log data of two wells are used SCRF

  7. Data Available • Well logs (Sw, Sonic, Phi) • Horizons • Well data • - Oil , gas and water flow rate • - BHP (Bottom hole pressure) SCRF

  8. Rock Physics Modeling Well Logs K and G (All Brine) Vp and Vs (Initial) K and Phi G and Phi Sonic Sw, Phi Gassmann’s Substitution Calculate Vp and Vs (All Brine) K and G (All Brine) Facies classification K and G (at Reservoir) Populate K ,G based on Phi K : Bulk Modulus G: Shear Modulus SCRF

  9. Facies Classification Shale Brine Sand Vp / Vs Shaly Sand Oil Sand AI Vsh SCRF

  10. Rock Physics Modeling Well Logs K and G (All Brine) Vp and Vs (Initial) K and Phi G and Phi Sonic Sw, Phi Gassmann’s Substitution Calculate Vp and Vs (All Brine) K and G (All Brine) Facies classification K and G (at Reservoir) Populate K ,G based on Phi K : Bulk Modulus G: Shear Modulus SCRF

  11. Sensitivity Parameters in fluid substitution • Clay content • Salinity • Gas-oil ratio (GOR) • Pore pressure • The sensitivity of varying above parameters to variations in Response Response: Sum of seismic P-wave velocity after fluid substitution SCRF

  12. Experimental Design SCRF

  13. Results of fluid substitution Sensitivity to clay content Sensitivity to salinity 40 16000 20 0 15500 15000 Response Sensitivity to pore pressure Sensitivity to GOR 225 30 200 27 25 175 Clay content and GOR are the first and second most sensitive parameters in fluid substitution

  14. Rock Physics Modeling Well Logs K and G (All Brine) Vp and Vs (Initial) K and Phi G and Phi Sonic Sw, Phi Gassmann’s Substitution Calculate Vp and Vs (All Brine) K and G (All Brine) Facies classification K and G (at Reservoir) Populate K ,G based on Phi K : Bulk Modulus G: Shear Modulus SCRF

  15. Rock physics model Varying clay content and GOR (9 cases) SCRF

  16. Constant cement model Cement fraction Coordination number Clay content

  17. Fluid mixing • Seismic velocities depend on fluid saturation as well as saturation scale • Reservoirs with gas are very likely to show patchy behavior Sengupta ,2000 SCRF

  18. Effective pressure model Two effective pressure models are selected for sensitivity study SCRF

  19. Sensitivity Parameters in modeling 4D response • Clay content • Gas-oil ratio (GOR) • Coordination number • Cement fraction • Effective pressure model • Fluid mixing (Uniform or Patchy) • The sensitivity of varying above parameters to variations in Response Response: L1 Norm of change in seismic P-wave impedance after 4 years

  20. Experimental Design Total number of cases: 324

  21. Compare Methodology Dynamic modeling (1997-2001) Δ Pressure Δ Saturation P-wave impedance in 1997 and 2001 Rock physics modeling Difference in impedance SCRF

  22. Results P-wave impedance change in 4 years (m/s.kg/m3) Clay content = 0 % Clay content = 20 % SCRF

  23. Results Sensitivity to clay content Sensitivity to coordination number 9 7 5 40 20 0 Sensitivity to GOR Sensitivity to cement Response 3 5 1 225 200 175 Sensitivity to effective pressure model Sensitivity to fluid mixing Uniform Patchy Model 1 Model 2

  24. Conclusions and Future Work • Clay content is the most sensitive parameter in fluid substitution • Salinity and pore pressure have a lesser impact than clay content • Coordination number is the most sensitive parameter in modeling 4D response of Norne field • The result of this study will be used in joint inversion of time-lapse and production data of Norne field SCRF

  25. Acknowledgement • Statoil for data • Norwegian University of Science and Technology (NTNU) SCRF

  26. Conclusions and Future Work • Clay content is the most sensitive parameter in fluid substitution • Salinity and pore pressure have a lesser impact than clay content • Coordination number is the most sensitive parameter in modeling the time lapse seismic signature of Norne field • The result of this study will be used in joint inversion of time-lapse seismic and production data of Norne field SCRF

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