2. Testing survey resolution using Spectral Analysis Authors: Markham, S.L., Kivior, I., Vaughan, F.V., Yates, S. and Barnden S. EAGE Workshop on The Future of Non-Seismic Methods 12-15 October 2008, Manama, Bahrain

3. Table of Contents Introduction Theoretical Models: One layer Two layer Case Study: Central San Luis Basin MWT examples Conclusions

4. Theoretical Models: One and Two Layers One Layer; 50x50m, 100x100m and 500x500m grid spacing Two Layers; 100x100m, 200x200m and 500x500m grid spacing

5. One layer model: Basement

6. Profile view of one layer model

7. Simple one layer model: Basement at 1km and 5km

8. MWT plots for 50x50m grid Manual Multi-Window Test Grid Resolution 50x50m; Source Depth 1km Window Size Depth [m] 500 1000 1500 10 30 50 70 90 0

9. MWT plot for 50x50m grid, source depth 5km 5000m

10. Simple one layer model: Basement at 1km and 5km

11. MWT plots for 500x500m grid, source depth 1km 1000m

12. MWT plot for 500x500m grid, source depth 5km 5000m

13. Two layer model: Sedimentary layer

14. Profile view of 2 layer model

15. Two layer model: 100x100m grid, source depths 1 & 2km 1000m 2000m

16. Two layer model: 100x100m grid, source depths 4 & 5km 4000m 5000m

17. Two layer model: 200x200m grid, source depths 1 & 2km 1000m 2000m

18. Two layer model: 200x200m grid, source depths 4 & 5km 4000m 5000m

19. Two layer model: 500x500m grid, source depths 1 & 2km 1000m 2000m

20. Two layer model: 500x500m grid, source depths 1 & 2km 1000m 2000m

21. Two layer model: 500x500m grid, source depths 4 & 5km 4000m 5000m

22. Case study using survey acquired on behalf of USGS in Central San Luis Basin, Colorado, U.S.A.

23. Central San Luis Basin survey (USGS) Examples using the 200m line spacing dataset (40x40m grid) Traverse lines removed to simulate; 400m line spacing (80x80m grid) 800m line spacing (160x160m grid) 2000m line spacing (400x400m grid)

24. Location of test area

25. Location of MWT profile and manual stations 1234

26. MWT: Auto-ESA (40x40m)

27. MWT: Depth vs. Window Size at 4 points along profile (40x40m) 1 2 3 4

28. MWT: Example of spectrum at 417000mE (2)

29. MWT: Auto-ESA (80x80m)

30. MWT: Depth vs. Window Size at 4 points along profile (80x80m) 12 3 4

31. MWT: Auto-ESA (160x160m)

32. MWT: Depth vs. Window Size at 4 points along profile (160x160m) 12 3 4

33. MWT: Auto-ESA (400x400m)

34. MWT: Depth vs. Window Size at 4 points along profile (400x400m) 12 34

35. Cross-section derived from Seismic data

36. Examples of manual MWT at well locations in Middle East

37. MWT example at well location 1

38. Spectrum example at well location 1

39. MWT example at well location 2

40. Spectrum example at well location 2

41. Conclusions The resolution of the survey data has significant impact on ability to accurately define depths using spectral analysis High resolution surveys with line spacings of 200 and 400m are needed to image subtle intersedimentary horizons Widely spaced surveys of 1600 and 2000m are unlikely to resolve shallow features

42. References Bankey, V., Grauch, V., J., S., Webbers, A., and PRJ, Inc. (2005). Open File Report 2005-1200, USGS Kivior, I., Boyd, D., Shi, Z. and McClay, K., R., 1993, Exploration Geophysics, 24, 603-608. Spector, A. and Grant, F., 1970, Geophysics, 35, 293-302. Yates, S., Kivior, I., Damte, S., Markham, S., L. and Vaughan, F., 2008, in press.

43. Acknowledgements The data used for this study was made available for research purposes by the USGS.