SPE Distinguished Lecturer Program

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SPE Distinguished Lecturer Program
The SPE Distinguished Lecturer Program is funded
principally through a grant from the SPE
Foundation. The society gratefully acknowledges
the companies that support this program by
allowing their professionals to participate as
lecturers. Special thanks to the American
Institute of Mining, Metallurgical, and
Petroleum Engineers (AIME) for its contribution
to the program.
Society of Petroleum Engineers Distinguished
Lecturer Program www.spe.org/dl
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Realizing Full Potential of Hydraulic Fracturing
Damage Mechanisms and Mitigation

• Joseph A. Ayoub

Society of Petroleum Engineers Distinguished
Lecturer Program www.spe.org/dl
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Outline

• Typical damage processes impact on production
• Experimental investigation of Polymer based
  fluids
• Effect of breakers
• Conclusions

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Typical Effects with Impact on Productivity

• Permeable rock
• Stress dependency
• Inertial pressure losses, non-darcy flow
• Fracturing process
• Hydraulic/fluid invasion
• Mechanical
• Combined hydraulic and mechanical (increased
  capillary forces)
• Unbroken fracturing fluids within the fracture

Typically considered in isolation BUT How do they
mutually affect each other? Which are most
important??
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Fracture Cleanup Example

• Gas Reservoir
• Permeability 0.01 0.1 md
• Net pay 10 m
• Reservoir pressure 600 bar
• Fracture Parameters
• Half length 75 m
• Dimensionless conductivity 1 100
• Leakoff volume 15-60 m3
• Production Scenario
• Flowing bottom hole pressure limit 100 bar

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Numerical Approaches Reservoir Simulation
Loadwater after fracturing

• 3 Phases
• Non-darcy flow
• fracture
• Reservoir
• Stress-dependent Perm
• proppant
• Reservoir
• Non-newtonian fluid in the fracture

Permeability within fracture plane
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Case 1 No Damage
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Case 1 Only Hydraulic Damage
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Case 1 Only Hydraulic Damage

• Gas rate is practically not affected
• First to discuss Holditch 1979

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Adding Impact on Capillary Pressure in Damaged
Zone
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Another Source for Damage Residual Gel Within
Proppant Pack
Poor cleanup at fracture tips!
Can cause significant reduction in fracture
effectiveness
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Yield Stress Experimental Characterization

• JIPFracture Clean-up and Productivity
• Initiated in 2002 with six members

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Experimental Apparatus Flow Initiation Parallel
to the Filter Cake
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Flow Initiation of Crosslinked GuarLow Polymer
Concentration
FIP Flow Initiation Pressure. FIG Flow
Initiation Gradient
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Summary of Crosslinked Guar Results
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Cell Set up for Polymer Concentration Tests
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Summary of Crosslinked Guar Results
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Model of Polymer Concentration in
Proppant Pack
Filter
Cores
cake
Fluid at Initial Conc.
Proppant
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Interpretation of Crosslinked Guar Test Results
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Flow Initiation of Crosslinked Guar20 ppt
Encapsulated Breakers (EB)
Dispersed Randomly
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Flow Initiation of Crosslinked Guar 40 ppt EB
Layered in Filter Cake
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Summary of Crosslinked Guar ResultsEffect of
Breaker and Delivery Method
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Conclusions

• Polymer fluid yield stress effect reduces
  effectiveness of fracture treatments
• The polymer concentrates only in the filter cake
• High flow initiation gradients (yield stress) are
  observed when the filter cake dominates the flow
  path
• Breaker delivered into the filter cake is much
  more effective at reducing the yield stress than
  breaker randomly distributed a fluid loss agent
  that becomes a breaker would provide an ideal
  solution

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Acknowledgments

• S. Cobianco
• C. Emiliani
• T. Friedel
• M. Glover
• R. Hutchins

• M. Köhler
• G. Nitters
• D. Norman
• G. Turk
• F. Van der Bas

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Additional slides