High Resolution Carbonate Reef Interpretation Using Cross Well Data

1. High Resolution Carbonate Reef Interpretation Using Cross Well Data Thomas Morgan, Ph.D., Schlumberger Mike Raines*, Whiting Petroleum *formerly with Sandridge Energy

2. Sites: Michigan West Texas Focus: Gross Structure Internal Structure Depositional Environments

3. Geological Information Well Logs Geophysical Data Geological Interpretation

4. Michigan Silurian Reef • Single profile • Isolated pinnacle reef • Only one additional well • No surface seismic available

7. Tomographic Velocity Inversion • Picked Direct Arrivals • 3D Thin Layer Model • 3D Ray Tracing • Model Interfaces and Layer Parameters Described by Chebyshev Polynomials

9. Imaging • Kirchhoff Integral • Prestack Reflection Imaging • Depth • Dip Oriented and Aperture Limited • Ray Trace Travel Times from Tomographic Velocities • Angle Gather Output

11. 30 degrees 45 degrees 70 degrees

12. Interpretation Approach • Profile is in Depth • Exact depth tie at the wells • – no time to depth conversion needed • Resolution at the outcrop level – human scale geology • Geological Interpretation versus Geophysical Interpretation

14. Evaporites Reef Zone Grey Niagaran Burnt Bluff Carbonate

16. Bioherm

17. Organic Reef Bioherm

18. Organic Reef Bioherm

19. Organic Reef Bioherm Reef Rubble

20. Supratidal Island Organic Reef Bioherm

21. Tidal Flats Supratidal Island Organic Reef Bioherm

23. West Texas Permian Reef • Multiple profiles • More complicated structure • Better well control • Surface seismic available

24. Right Middle Left

26. ~ Reef Top Marker Near OWC

27. Stacked Mounds Shaley Lag Deposit ~ Reef Top (Erosional) On Lap Inter-Mound CO3 Debris Marker Near OWC

28. Stacked Mounds ~ Reef Top Inter-Mound CO3 Debris

29. Shaley Lag Deposit ~ Reef Top

30. Conclusions • Depth profiles provide unambiguous well ties • Resolution allows a truer look at the geology • Geophysical effects pushed down to smaller scale • Reservoir level geologic Interpretation is possible

31. High Resolution Interpretation of a Permian Reef Michael A. Raines, Sandridge Tertiary, LLC, Thomas R. Morgan*, Ph.D., Schlumberger Poster PDC P2, Station D1 Tuesday, October 27 at 11:40 a.m.

32. Acknowledgments: We would like to thank Sandridge Energy and Michigan Technological University for the use of the data. References: Bube, K., and R. Langan, 1999, On a continuation approach to regularization for crosswell tomography: 69th Annual International Meeting, SEG, Expanded Abstracts, 1295-1298. Liao, Q., and G. A. McMechan, 1997, Tomographic imaging of velocity and Q, with application to crosswell seismic data from the Gypsy Pilot Site, Oklahoma: Geophysics, 62, 1804-1811. Quan, Y., and J.M. Harris, 1997, Seismic attenuation tomography using the frequency shift method: Geophysics, 62, 895-905. Huh, M.H., L.I. Briggs, and D. Gill, 1977, Depositional Environments of Pinnacle Reefs, Niagaran and Salina Groups, Northern Shelf, Michigan Basin, in: Studies in Geology No. 5, Reefs and Evaporites – Concepts and Depositional Models, AAPG, J.H. Fisher ed.