1. A depth trend tool to assist the interpretation of seismic amplitudes Trond Anders Seland, Statoil Force seminar, NPD, Stavanger 28 th September, 2004

2. 2 Rock Models Seismic Signature Regional Well Data Geology Lithology/Fluid Experience Seismic Data Rock PhysicsSeismic Modelling , Vp,Vs Outline

3. 3 Rock Models Seismic Signature Regional Well Data Geology Lithology/Fluid Experience Seismic Data Rock PhysicsSeismic Modelling , Vp,Vs 1

4. 4 Rock Model Seismic Signature Regional Well Data Geology Lithology/Fluid Experience Seismic Data Rock PhysicsSeismic Modelling , Vp,Vs 2

5. 5 Rock Model Seismic Signature Regional Well Data Geology Lithology/Fluid Experience Seismic Data Rock PhysicsSeismic Modelling , Vp,Vs 3

6. 6 Seismic crossplot far P (near) gwc ? softhard P Intercept G Gradient RpRp  sin 2  P G RpRp 

7. 7 Blocked log data from a deepwater basin Blocked data: 47 sandstones with overlying shales from 10 wells

8. 8 Sandstone density, Vp and Vs vs. porosity Fluid: Brine Density, Vp and Vs strongly correlates to porosity The porosity is crucial for the outcome of the entire model Density, Vp and Vs will be computed with porosity as the main input parameter

9. 9 Mechanical compaction. Grain rearrangement – Grains move into tighter packing configurations, and correlates with the stress Brittle deformation – At high stress Plastic deformation – Grains deform under stress – Promotes further grain rearrangement Mechanical compaction. Modified Lander and Walderhaug model (1999)

10. 10 Quartz diagenesis

11. 11 Walderhaug quartz cementation model (1996) Main input parameters – Fraction of coated area – Quartz grain diameter – Fraction of quartz Temperature history – Heating rate – Initial temperature – Temperature gradient Temp. Time Temp. Time

12. 12 Burial history Rate of subsidence: 250m/Ma Temperature gradient: 4°C/100m  Heating rate: 10°C/Ma

13. 13 Chemical compaction 10°C/Ma1°C/Ma  Chemical compaction starts at about 2000m Generally: Quartz cementation starts at about 80 °C This basin: Temperature gradient: 4°C/100m

14. 14 Velocity-porosity models Wyllie et al. (1956) Raymer et al. (1980) Han (1986) Tosaya (1982) Eberhart-Phillips (1986) Krief et al. (1990) Nur (1998) Contact Cement Model Uncemented Sand Model or Modified Lower Hashin-Shtrikman Constant Cement Model Consolidated Sand Model or Modified Upper Hashin-Shtrikman

15. 15 Shale models Porosity: – Modified Lander and Walderhaug model – Normal, soft and hard P- and S-wave velocities: – Modified Krief model

16. 16 Depth trends Sandstone Shale Brine Sandstone Oil Sandstone Gas Sandstone Shale

17. 17 Depth trends (2)

18. 18 Crossplot screenshot

19. 19 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m)

20. 20 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m) Deeper (1800->2500)

21. 21 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m) Deeper (1800->2500) Harder shale

22. 22 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m) Deeper (1800->2500) Harder shale Higer porosity (20->24)

23. 23 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m) Deeper (1800->2500) Harder shale Higer porosity (20->24) Lower API (30->20)

24. 24 Crossplot study -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient Base case (1800m) Deeper (1800->2500) Harder shale Higer porosity (20->24) Lower API (30->20) Lower oil saturation (80->30)

25. 25 Crossplot study Base case (1800m) Deeper (1800->2500) Harder shale Higer porosity (20->24) Lower API (30->20) Lower oil saturation (80->30) Stiffer sandstone -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 -0.2-0.100.10.2 Intercept Gradient

26. 26 Summary Select depth only: Software computes expected porosities, elastic parameters and seismic amplitudes Lithology and fluid parameters can easily be modified