Pitfalls in Rock Properties and Lithology Prediction in Dolomite

1. Pitfalls in Rock Properties and Lithology Prediction in Dolomite John Logel Anadarko Canada Corp

2. Objective • To demonstrate that subtle but powerful seismic phenomenon can substantially harm your seismic data and your interpretation • TLC processing and “new” algorithms may not be enough to help • Quality control, detailed investigation of data, and proper prospecting and risk are critical.

3. Outline • Dolomite as the reservoir • The surprise prospect and well • The Mistie • The VSP results • The enemy (High order interbed multiples, Q) • Possible fixes and conclusions

4. Hydrothermal Dolomite Process Davies, et al.

5. Shale 2.58 g/cc 5800 P m/s 2000 S m/s 15000 AI 5200 SI 2.9 Vp/Vs 21 Gpa Bulk 7 Gpa Shear Dolomite 2.87 g/cc 7000 P m/s 3960 S m/s 20090 AI 11365 SI 1.77 Vp/Vs 95 Gpa Bulk 45 Gpa Shear Rock Properties and economic properties • Limestone • 2.71 g/cc • 6450 P m/s • 3440 S m/s • 17479 AI • 9322 SI • 1.88 Vp/Vs • 77 Gpa Bulk • 32 Gpa Shear • 50 MM.day IP • 50B – 3 TCF UR • high spacing • 10 MM/day IP • 10 B – 50 B UR • low drainage • 0 MM /day IP • 0 BCF • No more drilling AI Dolo with 10 % por = LS 6% por = Shale Vp/Vs changes less

6. Tuning curve for “Typical” Dolomite reservoir 0 10 20 30 40 50 amp 4 to 20 ms zone of anomolous amplitude For 45 Hz Dom freq isochron

7. Dolomite Zero Offset Modeling Dolomite Porosity Development Dolomite Tight Porous

8. Processing Highlights • Boutique TLC Processing • PSTM • 2 Passes of velocities • 2 passes and 2 different Algorithms of De-multiple (Radon and Inquisitor hyperbolic) • Controlled Amp and Phase QC • Controlled Scaling

9. 3 Window Amp extraction NO CAPP

10. 3 Window Amp extraction CAPP (Deep Win Scaler)

11. 3 Window Amp extraction Full CAPP

12. LambdaRho - MuRho Interpretation Template Crossplot Guide LambdaRho - MuRho Interpretation Template Crossplot Guide Gas 1:1 Gas 1:1 125 125 2:1 2:1 100 100 POROUS POROUS TIGHT TIGHT DOLOMITE DOLOMITE LIMESTONE LIMESTONE .gm/cc .gm/cc Calcareous Wet Calcareous Wet Gas Gas MuRho Gpa MuRho Gpa 50 50 Shales Shales SAND SAND SHALE SHALE Clastic Clastic Shales Shales 0 0 50 100 150 200 250 50 100 150 200 250 0 0 LambdaRho GPa .gm/cc LambdaRho GPa .gm/cc 2005031a- 8 LMR Interpretation Methodology Goodway etal.

13. Co-rendered Amplitude and Linament detection

14. Prospect Waveform classification map Prospect And leads

15. Pre-drill Analysis Prospect Analogue Well lambda Analogue Mu Ratio diff Prospect

16. Drill the Well!!!!

17. Post-Drill !! Analogue Prospect GR dt rhob GR dt rhob

18. Raw Synthetic tie CC= .29 Zone of Interest

19. What Now ??

20. Petrophysicist

22. Post edit Synthetic tie CC=.4 Zone of Interest

23. Processing Geophysicist

24. Other Problems, Pitfalls and Corrections • Multiples • Q (attenuation) VSP

25. VSP showing potential sources of Interbed multiples High velocity Low Velocity/Laminated Basin Fill Shales Inside Corridor Stack Outside Corridor Stack High Velocity Zone of Interest

26. VSP – Data comparison Zero (corridor) VSP stack Inside (multiple) stack seismic data Zone of Interest

27. VSP (downgoing colour – upgoing WVA) with Multiples Interbed multiples First arrivals Interbed multiples

28. Elastic Modeling Comparison Elastic Model 90 degrees Elastic Model Raw seismic Logs synthetics

29. Q (attenuation) • “Q” is the attenuation of frequency and the changes in phase because of it. • Shales or other “soft” material are most Q prone • Laminated material are also very Q prone • If it can be determined it can be corrected (difficult)

30. Wavelet extraction and response Extracted wavelet including shallow Extracted wavelet deep Theoretical response

31. Processed VSP and Q computation Spectral Ratio Method Drift Correction Method

32. Q Application correct qcomp orig

33. Q application and Amplitude Envelope Corrected Qcomp Orig

34. Final tie with synthetics validation VSP zos corrected model mult original

35. Questions about Multiples???? • Shouldn’t they be adequately attenuated? • Aren’t they too low of amplitude to worry about? • Aren’t they “constant”? • Shouldn’t you be able to differentiate Multiples from reservoir by a different AVO response? • Doesn’t the stack take care of it?

36. Questions about Multiples???? • Shouldn’t they be adequately attenuated? • Aren’t they too low of amplitude to worry about? • Aren’t they “constant”? • Shouldn’t you be able to differentiate Multiples from reservoir by a different AVO response? • Doesn’t the stack take care of it?

37. 2D expanding models Primaries only Primaries and Multiples

38. 2D expanding models Primaries only Primaries and Multiples

39. Questions about Multiples???? • Shouldn’t they be adequetely attenuated? • Aren’t they too low of amplitude to worry about? • Aren’t they “constant”? • Shouldn’t you be able to differentiate Multiples from reservoir by a different AVO response? • Doesn’t the stack take care of it?

40. AVO response for Dolomite Reservoir Reservoir AVO response CLASS IV

41. Seismic data showing horizons, multiples and VSP VSP no decon Pri & mult VSP decon Prim only Horizons Multiples

42. Zoom-in on multiple and logs

43. Seismic gathers showing primaries and multiples 2000 -2000

44. De-Multiple “Fixes” • Inquisitor Hyperbolic transform • High resolution Radon • Hybrid Radon • Inverse Scattering Subseries • Gabor decon (radial trace domain) • Wavelet Transforms • Forensic Audiology • Discrete Fourier transform • target oriented DECON • Mapping ** Discussed in this presentation

45. Elastic Model gather with Hyperbolic transform velocity Porosity Multiple

46. Dominant Principal Comps

47. Principal Comps recombined Original De-Multipled

48. Zone specific DFT Amp Primary Dominant Freq Multiple Dominant Freq Multiple contaminated Primaries Phase

49. Map of first Dominant Frequency

50. Target specific Gap decon Original Section Original De-multipled De-Multipled Section