1. Jun Lu, Geomechanical engineer
Daniel W.H. Su, Sr. Geomechanical engineer
Greg J. Hasenfus, Sr. Geomechanical engineer
Mark Van Dyke, Geologist
Luke Stull, Geologist

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
Longwall production
footage per week
240
124
232
142
115
194
323
Panel 21—SS fraced
344
24
106
306
338
230
Panel 20—SS not fraced

5. Objective
To compare and evaluate two hydraulic fractruing techniques
which were employed to mitigate the impact of a massive
sandstone channel on two successive longwall faces.

6. Geologic Reconnaissance
Sandstone Intrusion Encountered During Development
 In-Mine Core Drilling
 Surface Core Drilling
 Gas Well E-Logs
 Stratascope Observations
 In-Mine Mapping
Sandstone
Pittsburgh
Main Bench
Stopping

7. Geologic Reconnaissance
Frac horizion 15ft above base of
sandstone
5 Feet

8. Frac Hole Locations
Panel 22
Hydraulic
Fracture Hole
Surface
Corehole

9. Frac Process
 Frac holes drilling
 Perforations
 Water fracing

10. Comparison of Panel 22 vs 21
Frac hole numbers:
Panel 22: 3
Panel 21: 4
Water usage:
Panel 22: 42,000 gallons/hole, 35 barrels/minute
Panel 21: 14,000 gallons/hole, 25 barrels/minute
Projected pancake fractures:
Panel 22: 600 ft E-W, 400 ft N-S
Panel 21: 250 ft E-W, 150 ft N-S

11. Panel 22
Panel 21

12. 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

13. 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

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

15. Mining Direction
Correlation among the hydraulic fracturing hole locations, the LVA cavity
formation predictions, and the observed face conditions in Panel 22.
Face Monitoring and Evaluation

16. Panel 22
Panel 21
Mining Direction
Mining Direction

17. Face Monitoring and Evaluation
LVA: Time-Weighted Average Pressure (TWAP)
Panel 22
Panel 21

18. Face Advance Rate at Panel 21
(11.2 ft/shift)
Face Advance Rate at Panel 22
(15.6 ft/shift)
Longwall Productivity

19. Rock Delay at Panel 21
(110 min./shift)
Rock Delay at Panel 22
(27.5 min./shift)
Longwall Rock Delay

20. Conclusions
 Improved hydraulic fracturing technique
 Successfully employed LVA software
 Mitigated the impact of the massive sandstone channel
 Increased productivity
 Improved safety

21. Thanks!
Questions?