1. 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
Longwall production
footage per week
344
24
106
306
371
338
230

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
Trough of
Sandstone
Channel at
Wall # 29
Base of Sandstone
INBY OUTBYWALL
#33
WALL
#27
Drawslate
Pittsburgh Seam
5Feet
Vertical Scale

10. Frac Hole Locations and Frac Stage Horizons

11. Frac Process
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. Frac Process
Water fracing was employed

13. Frac Process
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 3.10
Itasca Consulting Group, Inc.
Minneapolis, MN USA
©2006 Itasca Consulting Group, Inc.
Step 11503 Model Perspective
16:38:18 Thu Jul 26 2012
Center:
X: 2.000e+000
Y: 3.860e+002
Z: 1.400e+001
Rotation:
X: 0.000
Y: 0.000
Z: 90.000
Dist: 1.361e+003 Mag.: 18.2
Ang.: 22.500
Job Title: F-21 Sandstone Frac-After
View Title:
Zone Extra 1
Magfac = 1.000e+000
Live mech zones shown
Gradient Calculation
1.9448e+002 to 5.0000e+002
5.0000e+002 to 1.0000e+003
1.0000e+003 to 1.5000e+003
1.5000e+003 to 2.0000e+003
2.0000e+003 to 2.5000e+003
2.5000e+003 to 3.0000e+003
3.0000e+003 to 3.5000e+003
3.5000e+003 to 4.0000e+003
4.0000e+003 to 4.3785e+003
Interval = 5.0e+002
FLAC3D 3.10
Itasca Consulting Group, Inc.
Minneapolis, MN USA
©2006 Itasca Consulting Group, Inc.
Step 15221 Model Perspective
16:37:57 Thu Jul 26 2012
Center:
X: 2.000e+000
Y: 2.138e+002
Z: 1.400e+001
Rotation:
X: 0.000
Y: 0.000
Z: 90.000
Dist: 1.361e+003 Mag.: 18.2
Ang.: 22.500
Job Title: F-21 Sandstone Frac-Before
View Title:
Zone Extra 1
Magfac = 1.000e+000
Live mech zones shown
Gradient Calculation
1.4037e+002 to 5.0000e+002
5.0000e+002 to 1.0000e+003
1.0000e+003 to 1.5000e+003
1.5000e+003 to 2.0000e+003
2.0000e+003 to 2.5000e+003
2.5000e+003 to 3.0000e+003
3.0000e+003 to 3.5000e+003
3.5000e+003 to 4.0000e+003
4.0000e+003 to 4.3785e+003
Interval = 5.0e+002
Flac3D Model
Without Frac
Massive
Sandstone
Clayey Shale
Longwall face
FLAC3D 3.10
Itasca Consulting Group, Inc.
Minneapolis, MN USA
©2006 Itasca Consulting Group, Inc.
Step 15221 Model Perspective
14:55:06 Wed Jul 18 2012
Center:
X: 1.585e+000
Y: 2.107e+002
Z: 8.023e+000
Rotation:
X: 0.000
Y: 0.000
Z: 90.000
Dist: 1.361e+003 Mag.: 18.2
Ang.: 22.500
Job Title: F-21 Sandstone Frac-Before
View Title:
Zone Extra 1
Magfac = 1.000e+000
Live mech zones shown
Gradient Calculation
1.9448e+002 to 5.0000e+002
5.0000e+002 to 1.0000e+003
1.0000e+003 to 1.5000e+003
1.5000e+003 to 2.0000e+003
2.0000e+003 to 2.5000e+003
2.5000e+003 to 3.0000e+003
3.0000e+003 to 3.5000e+003
3.5000e+003 to 4.0000e+003
4.0000e+003 to 4.3785e+003
Interval = 5.0e+002
Massive
Sandstone
Clayey Shale
Longwall face
Shear stress, psi
With Frac Frac horizon
15 ft

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 frac hole 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
240
124
232
142
115
194
323
F21—SS fraced
344
24
106
306
338
230
F20—SS not fraced

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

25. Thanks!
Questions?