Daniel W.H. Su, Sr. geomechanical engineer Greg J. Hasenfus , Sr. geomechanical engineer

1. Impact of a Massive Sandstone Channel on a 1500-Foot (457-Meter) Wide Longwall Face – Mitigation and Evaluation Daniel W.H. Su, Sr. geomechanical engineer Greg J. Hasenfus, Sr. geomechanical engineer Luke Stull, geologist Jun Lu, geomechanical engineer Mark Van Dyke, geologist Stephen Morgan, geologist Paul Kelley, mine engineer Don Teter, project engineer

2. Outline Introduction Objective Geology/Geologic Reconnaissance Hydro Frac Hole Locations and Frac Process Flac3D Models Longwall Visual Analysis (LVA) Monitoring Face Monitoring and Evaluation Conclusions

3. Introduction

4. Introduction Sandstone Intrusion Encountered During Development

5. Introduction Sandstone Intrusion Encountered During Development Base of Sandstone Channel

6. Introduction F20 Longwall Panel Problems • Delayed caving behind shield supports • Massive sandstone pot-outs in front of shields • Increased risk to personnel • Delayed Production 24 306 106 230 371 344 338 Longwall production footage per week

7. Objective To evaluate the effectiveness of the hydraulic fracturing program and the validity of Longwall Visual Analysis (LVA) software to mitigate the impact of a 1, 000-foot (305-meter) wide massive sandstone channel on a 1,500-ft-wide (457-meter-wide) longwall face.

8. Geologic Reconnaissance • In-Mine Core Drilling • Stratascope Observations • In-Mine Mapping • Primary Stress Orientation • Rock Lab Testing Average Axial Compressive Strength 8283 psi

9. Geologic Reconnaissance WALL #27 INBY OUTBY WALL #33 Base of Sandstone Trough of Sandstone Channel at Wall # 29 Vertical Scale Drawslate 5 Feet Pittsburgh Seam

10. Frac Hole Locations and Frac Stage Horizons

11. FracProcess Perforations were shot into the casing at the targeted horizons to pre-fracture the sandstone. The estimated shot penetration into the borehole surface was about 26 to 30 inches (0.66 to 0.76 meter).

12. FracProcess Water fracingwas employed

13. FracProcess Fracing result Initial break Shut-in

14. Outline Introduction Objective Geology/Geologic Reconnaissance Hydro Frac Hole Locations and Frac Process Flac3D Models Longwall Visual Analysis (LVA) Monitoring Face Monitoring and Evaluation Conclusions

15. Flac3D Model Frac horizon With Frac Without Frac Shear stress, psi 15 ft Massive Sandstone Massive Sandstone Clayey Shale Clayey Shale Longwall face Longwall face

16. Longwall Visual Analysis (LVA) LVA was installed to track the face pressure and cavity formation index. Cavity Risk Index (CRI)

17. Face Monitoring and Evaluation To evaluate the effectiveness of the hydraulic fracturing program and the validity of LVA software, daily face monitoring over a 4-week period was conducted. Based on the collected information, the correlations among the observed face conditions, the hydro frachole locations and the LVA cavity formation prediction were analyzed. Underground Observation Hydraulic Fracturing Longwall Visual Analysis

18. Ming Direction

19. Dec. 20, 2011

20. Face Monitoring and Evaluation

21. Face Monitoring and Evaluation

23. Face Monitoring and Evaluation Longwall production footage per week F20—SS not fraced F21—SS fraced 24 323 194 124 232 115 306 106 230 240 142 344 338

24. Conclusions • Successful application of hydraulic fracturing technique. • Successful application of LVA software. • Improve safety and increase productivity.

25. Thanks!Questions?