1. Analogs for Fault-controlled Ordovician Dolomite Reservoirs, Appalachian Basin: Geological and geophysical characterization of Central Kentucky outcrops
David C. Harris
Kentucky Geological Survey
Clay A. Wilcox
William F. Reid
Department of Geological Sciences
University of Kentucky

2. Outline Outcrop analogs: petrography and geochemistry
MS thesis by Clay Wilcox
Seismic reflection work
MS thesis by Bill Reid
Recently drilled corehole at Stoner Branch locality

3. Acknowledgements New York State Energy Research and
Development Authority
U.S. Department of Energy, National Energy
Technology Laboratory
Triana Energy, Inc.

4. Outcrop Project Goals
Characterize shallow Ordovician tectonic dolomites to improve exploration strategies
Approach: petrography, geochemistry, shallow high-resolution seismic, integration with New York reservoirs

5. Central Kentucky Study Area

6. Upper and Middle Ordovician Stratigraphyb N A m e S y / D k F B u L w d . v K x H Q T R J
Upper and Middle
Ordovician
Stratigraphy
Units affected by
fault-controlled
dolomitization

7. Structural Features Northern boundary fault of Rome Trough
Left-lateral wrench fault system
Central Ky. Mineral District

9. Lightbulb Sample Index

10. Saddle Dolomite, Clark Co., Ky.

11. S t o n e r B r a n c h D o l o s t o n e S a m p l e L o c a l i t y1 4 6 8 2 5 3 9 7 . 2 5 . 5 . 7 5 1
Mile S t o n e r B r a n c h D o l o s t o n e S a m p l e L o c a l i t y I n d e x

12. Ordovician Outcrops Petrography: conventional and CL
Geochemical techniques
oxygen and carbon stable isotopes
microprobe (trace elements)
Cores: continuous core through Trenton and Black River to top Knox
MS theses by Clay Wilcox and Bill Reid

13. Petrography Multiple generations of dolomite and calcite
Early dolomite: euhedral rhombs, replacive, non-Fe with some Fe zoning, luminescent
Later calcite cement, non-Fe to Fe
Late dolomite: Fe-rich, saddle dolomite, fills pores and replaces other grains/cement, non-luminescent

14. Early Dolomite

15. Multiple dolomite and calcite generations

16. Late dolomite

17. Late dolomite / calcite cement relationships

18. Stable Isotope Data –Early Dolomite, Lightbulb

19. Stable Isotope Data – Saddle Dolomite, Lightbulb

20. Stable Isotope Data – Stoner Branch

21. Stoner Branch Seismic Location Map
USGS
1 Allen
CNR Core
Location
LINE 1
LINE 2
LINE 3
LINE 4

22. Seismic imaging of dolomites
Data collected at lightbulb and Stoner Branch
P-wave and S-wave (shear) data
Data used to locate corehole

23. Line 1B Shear Wave Core Location Depth 23m 40m 58m 76m
Line length: 240 meters KY
River
Fault

24. Line 1A (P-wave) N S
Line length: 240 meters
Extent of
Dolomitization

25. Line 3B (shear wave) S N Extent of Dolomitization
Line length: 154 meters

26. Stoner Branch Corehole
Provide data on vertical distribution of dolomite
Evaluate dolomite in Black River
CNR drilled continuous HQ and NQ core from 27 to 1005 ft (306m); TD reached Oct. 23
Penetrated several small faults in shallow section
Penetrated Ky. River Fault Zone in the Black River: 175 ft (53m) of fractured limestone and breccia
TD in Knox on footwall, 280 ft high to downthrown block

27. Stoner Branch Well Location

28. CNR 3-04 Allen

29. SW NE Subsea Depth <507FT> Garrard Siltstone
960 GR
200 30
CNPOR
-10 2
RHOB 3
GAMMA_NEU
200 30
Garrard Siltstone
860
20 ft faulted out in
Garrard/Clays Ferry
100
Clays Ferry Formation
760
200
Trenton Ls
660
300
560
400
460
500
Black River Group
360
Pencil Cave Bentonite
600
260
280 ft faulted out in
Black River/Wells Creek
700
160
800 60
900
-40
1000
Wells Creek Dolomite
-140
1100
St. Peter Sandstone
-240
Knox Group
1200
-340
1300
ROME OIL & GAS CO
COLUMBIA NATURAL RES LLC
ALLEN JAMES B
ALLEN JAMES B JR 1
3-04

30. Preliminary Core Observations
Dolomitization limited to upper 220 ft: Trenton and Black River not pervasively dolomitized along fault
Fabric-selective dolomitization present in Trenton
Breccias in fault zone are dolomitized- but very limited alteration outside of fault zone in deeper section

31. Calloway Creek dolomite 49-53 ft

32. Trenton Limestone ft

33. Black River fault breccia with multiple calcite generations 823 ft

34. Black River fault breccia 847 ft

35. Black River breccia with sphalerite 698 ft

37. Fault Breccias
Calcite, dolomite, sphalerite, barite, pyrite mineralization present
Abundant evidence of multiple reactivation
Cross-cutting relationships and structural features will allow relative timing of fault movement and mineralization to be determined

38. Conclusions
Distribution, petrography and geochemistry of central Ky. Ordovician dolomites suggests hydrothermal origin
Complex diagenetic history, with multiple dolomitization events
Facies selectivity differs for different dolomite types
Fault conduits are primary control on distribution, but other factors control alteration zones

39. Final Project Review
PTTC-sponsored core workshop and final project review: Spring, 2005
KGS Core and Sample Repository, Lexington, Kentucky
Optional field trip if there is interest