Table Of ContentHydraulic
Fracturing
Emerging Trends and Technologies in
Petroleum Engineering
Series Editor
Abhijit Y. Dandekar
PUBLISHED TITLES:
Hydraulic Fracturing, Michael Berry Smith and Carl T. Montgomery
Wax Deposition: Experimental Characterizations, Theoretical Modeling, and
Field Practices, Zhenyu Huang, Sheng Zheng, H. Scott Fogler
Hydraulic
Fracturing
Michael Berry Smith
Carl T. Montgomery
Boca Raton London New York
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This book is dedicated to all the pioneers that developed the concepts
and physics that we use daily to design and execute hydraulic
fracturing treatments. Many of these pioneers have been identified
in the “Legends of Hydraulic Fracturing” program and include
Claude E. Cook, Jr.
Robert R. Hannah
Ronald P. Nordgren
Francis E. Dollarhide
Larry J. Harrington
Tomas K. Perkins
Jacque L. Elbel
George C. Howard
Mike Prats
C. Robert Fast
J.L. Huitt
H. K. van Poollen
Ken Nolte
Steven Holditch
Héber Cinco Ley
Contents
Series Preface .......................................................................................................xix
Preface .................................................................................................................xxiii
Chapter Abstracts ..............................................................................................xxv
Authors .............................................................................................................xxxiii
1. History, Introduction, and How a Treatment Is Conducted ..................1
Introduction ......................................................................................................1
Fracture Geometry ...........................................................................................8
Fracturing Fluids .............................................................................................9
Proppants ........................................................................................................10
Surface Equipment and Setup .................................................................11
Pumps .........................................................................................................14
Blenders ......................................................................................................17
Proppant Handling ...................................................................................18
Iron ..............................................................................................................19
Auxiliary Equipment ................................................................................20
Sensors ........................................................................................................22
Wellhead Isolation Tools ..........................................................................23
Offshore Equipment .................................................................................23
Treatment Design ...........................................................................................25
Modern Treatment Design Process .............................................................29
Additional Comments ...................................................................................30
References .......................................................................................................31
2. Definitions and Simple Geometry Models .............................................33
Introduction ....................................................................................................33
What Is Fracturing? .......................................................................................34
Why Fracture? ................................................................................................36
Damage Bypass .........................................................................................36
Increased Productivity .............................................................................37
Reservoir Management ............................................................................38
Treatment Design Variables .........................................................................41
Wellbore Breakdown ................................................................................42
Material Balance ........................................................................................42
Fracture Height, H ....................................................................................42
Fluid Loss (C and V ) ............................................................................45
Spurt
Fracture Width ...........................................................................................47
P (Net Pressure) .....................................................................................51
Net
References .......................................................................................................56
vii
viii Contents
3. Design Variables ...........................................................................................59
Design Parameters: Fracture Height ...........................................................59
Effect of Closure Stress on H ..................................................................62
F
Effect of Formation Thickness ................................................................68
Effect of Modulus Contrasts on Height Growth...................................71
Other Variables Affecting Fracture Height ...........................................73
Design Parameters: Modulus (E) .................................................................75
Effects of Modulus ....................................................................................76
Typical Values ............................................................................................79
Young’s Modulus from Sonic Logs .........................................................80
Design Parameters: Fluid Loss (“C” and Spurt) ........................................80
Fluid Loss Coefficient, C ..........................................................................81
C (or C ) ................................................................................................84
III Wall
Effect of Proppant .....................................................................................88
Fluid Loss Additives .................................................................................89
C from Fracturing Pressure Analysis ....................................................90
Spurt Loss ...................................................................................................90
Total or Combined C .................................................................................93
Fracture Tip Effects, Apparent Toughness, K .....................................94
Ic
Design Parameters: Frac Fluid Viscosity .............................................101
Design Parameters: Pump Rate.............................................................102
Design Parameters: Summary ..............................................................104
References .....................................................................................................105
4. Rock Stresses ...............................................................................................109
Introduction ..................................................................................................109
History ...........................................................................................................111
Vertical Stress ...............................................................................................111
Horizontal Stress ..........................................................................................112
Gravity Stress ...........................................................................................113
Effect of Reservoir Pressure ..................................................................118
Tectonics ...................................................................................................119
In Situ Stress Direction ...............................................................................123
Fracture Orientation and Azimuth ......................................................123
In Situ Stress Differences ............................................................................127
Stress Barriers for Height Containment: Δσ ...........................128
Shale–Sand
Stress Barriers for Height Containment—Δσ —
Shale–Sand
How Big? .........................................................................................129
Measured Stress Differences .................................................................129
Secondary Fractures ...............................................................................130
Secondary Fracture: “T” Fracture .........................................................130
Secondary Fracture: Natural Fractures ................................................131
In Situ Stress Measurement ........................................................................132
Injection Tests ..........................................................................................132
Shear Wave Sonic Log Data ...................................................................133
Contents ix
Proppant Stress ............................................................................................134
Wellbore Breakdown ...................................................................................135
References .....................................................................................................139
5. Petrophysics .................................................................................................141
Depth .............................................................................................................141
Primary Logs ................................................................................................142
Temperature .............................................................................................143
Density Neutron ......................................................................................143
Density Log .........................................................................................143
Neutron Log ........................................................................................144
Effective Porosity ................................................................................144
Density–Neutron Crossover .............................................................144
Gamma Ray .............................................................................................145
Sonic Logs ................................................................................................147
Acoustic Log (Compressional Wave Velocity) ................................147
Static versus Dynamic Modulus ......................................................149
Shear-Wave Sonic Logs ......................................................................150
Effects of Anisotropy .........................................................................152
Gas Effect on V ..................................................................................153
P
Image Logs ...............................................................................................154
References .....................................................................................................157
6. Post-Frac Performance ...............................................................................159
Fracture Length or Conductivity? .............................................................162
Fracture Length: X .................................................................................163
f
Equivalent Wellbore Radius .......................................................................165
Folds of Increase ...........................................................................................167
Drainage Boundary Effects ...................................................................173
Acid ................................................................................................................175
Transient Flow ..............................................................................................176
References .....................................................................................................183
7. Treatment Scheduling ...............................................................................185
Introduction ..................................................................................................185
Perfect Support Fluids .................................................................................185
Pad Stage for Perfect Support Fluids ....................................................189
Banking Fluids .............................................................................................189
Pad Stage for Banking Fluids ................................................................192
Tip Screen-Out Fracturing ..........................................................................192
Pad Volume and Proppant Schedule for Tip Screen-Out Designs ......194
Time–Temperature Fluid History ..............................................................215
Unexpected Design Flaws or “Gotchas” ..................................................216
References .....................................................................................................218
Additional References .................................................................................219
x Contents
8. Frac Pressure Analysis ...............................................................................221
History ...........................................................................................................221
Similarity to Pressure Transient Analysis ................................................222
Closure Pressure ..........................................................................................224
Microfrac Tests .........................................................................................229
Step-Rate Injection Test ..........................................................................230
Pump-In/Decline Testing ......................................................................231
Pump-In/Decline Data Plus Step-Rate Data .......................................267
Pump-In/Flowback Stress Test .............................................................267
Treating Pressure (P ) Analysis ...............................................................270
Net
Nolte–Smith Log–Log Interpretation ...................................................271
General Interpretation ............................................................................278
Quantitative Interpretation ....................................................................283
What Can We Learn? ..............................................................................286
PDL Analysis ................................................................................................286
Fluid Efficiency ........................................................................................289
ΔP*, G Plot Analysis ................................................................................290
Analysis for Reservoir Parameters (After-Closure Analysis) ...............296
Importance of Derivative .......................................................................301
Acknowledgment .........................................................................................301
Appendix A: Application and Examples ..................................................304
Low Permeability .........................................................................................304
Small-Volume Pump-In/Decline Test ..................................................305
“Low k” Example................................................................................306
Step-Rate Test ...........................................................................................306
Pad Fluid Minifrac ..................................................................................306
Moderate/High Permeability .....................................................................314
Appendix B: G Function .............................................................................321
Q : Fluid Loss Rate ...................................................................................321
Loss
Fracture Stiffness .........................................................................................325
G Function .....................................................................................................328
G Function Plot for ΔP* ...............................................................................330
References .....................................................................................................331
Additional References .................................................................................334
9. Engineering the Fluid ................................................................................335
Introduction ..................................................................................................335
History ...........................................................................................................337
Types of Fracturing Fluids .........................................................................342
Water Frac .................................................................................................344
Linear Gel .................................................................................................344
Cross-Linked Gels ...................................................................................344
Oil-Based Fluids ......................................................................................345
Foam/Polyemulsions ..............................................................................345
