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Hydraulic Fracture Complexity and Treatment
Design in Horizontal Wells
Craig Cipolla
VP of Stimulation Technology
Carbo Ceramics/StrataGen Engineering
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Outline
Fracture complexity
Proppant distribution
Reservoir simulation (horizontal wells with complexfractures growth)
Effect of fracture conductivity
How much conductivity is needed?
Effect of modulus on network fracture conductivity
Effect of staging
Effect of network fracture complexity (i.e. spacing)
Effect of permeability
Summary & conclusions
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Simple Planar Fracture Growth
Simple Fracture
Simple Fracture
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Predictable Proppant Distribution
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Complex Planar Fracture Growth
Complex Fracture
Complex Fracture
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Complex Growth, Fissure Opening
Complex Fracture
With Fissure Opening
Complex Fracture
With Fissure Opening
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Network Fracture Growth
Complex Fracture
Network
Complex Fracture
Network
Unpredictable Proppant Transport?
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Fracture Complexity & Natural Fractures
NaturalFracturesHydraulic
Fractures
NaturalFracturesHydraulic
Fractures
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Grasshopper, Now You Must Choose!
Simple or Complex?
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Proppant Distribution
(network fracture growth)
reference SPE 115769
Proppant volumes probably insufficient to effectively prop large networksNetwork fracture conductivity likely dominated by un-propped fractures
Proppant may not be effectively transported into complex networks
Un-propped fracture conductivity a key factor in well productivity
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Proppant Distribution
Vertical Proppant Distribution
Arch dimensions and stress on proppant
based on SPE 119350 War inski
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Proppant DistributionVertical Proppant Distribution in Primary Fracture
*reference Britt SPE 102227 and SPE DL presentation 2007-2008 Series
C*fD-vertical = kfwf/khf-unpropped?
CfD= kfwf/kxf
C*
fD-vertical = kfwf/khf-propped?
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Production Modeling in Shale-Gas Reservoirs
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Comparison WellsBarnett Horizontal Completions
Well A
2,600 ft lateral
Four frac stages
o 670 klbs (40/70-sand), 120,000 bbls
o 700 ft between perforation clusters
SRV = 1,880x106 ft3 (Microseismic fracture mapping)
Well B
2,600 ft lateral
Two frac stages
o 830 klbs (40/70-sand), 117,000 bbls
o 500 ft between perforation clusters
SRV = 2,017x106 ft3 (Microseismic fracture mapping)
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Stimulating Horizontal Wells
Symmetry for Reservoir Simulation
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Impact of Fracture Conductivity
Pressure distribution after 3 months
400 ft main fracture spacing, 100 ft networkfracture spacing, 2 mD-ft network conductivity
2 mD-ft primary fracture conductivity
Pressure (psi) Pressure (psi)
Pressure (psi)Pressure (psi)
Pressure distribution after 1 yr
100 mD-ft primary fracture conductivity 400 ft
Insufficient fracture conductivity
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Impact of Primary Fracture Conductivity
400 ft main fracture spacing and 100 ft network fracture spacing
Barnett HZ well
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Impact of Network Fracture Conductivity
300 ft primary fracture spacing, 100 ft network fracture spacing
Well A Well B
300 ft primary fracture spacing, 100 ft network fracture spacing
Well A Well B
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How Much Fracture Conductivity is Needed?
Results for 50 ft fracture spacing
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network conductivity required to achieve 90% of maximum 1st productionNetwork Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network conductivity required to achieve 90% of maximum 1st production
25
212
0.4
3.5
71
224
2.8
22
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network conductivity required to achieve 90% of maximum 1st productionNetwork Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network Conductivity Required to Achieve 90% of 1st
-year Production
0.1
1
10
100
1000
FractureCon
ductivity(mD-ft)
0.0001 mD
0.01 mD
Small Network
Uniform Network
Conductivity
Small Network
Infinite
Conductivity
Primary Fracture
Large Network
Uniform Network
Conductivity
Large Network
Infinite
Conductivity
Primary Fracture
Network conductivity required to achieve 90% of maximum 1st production
25
212
0.4
3.5
71
224
2.8
22
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0.1
1
10
100
1000
10000
0 2000 4000 6000 8000
Closure Stress, psi
ReferenceCondu
ctivity,md-ft
0.1 lb/sq ft bauxite
0.1 lb/sq ft Jordan sand,
or displaced un-propped
Un-Propped & Partially Propped Fracture Conductivity
How Much Conductivity can be Achieved?
Uniform Network Conductivity
Infinite Conductivity
Primary Fracture
Adapted from SPE 60236, 74138
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Un-Propped Fracture Conductivity
Effect of Modulus
0.01
0.1
1
10
100
1000
0 2000 4000 6000 8000
Stress (psi)
Conductivity(mD-ft)
E=6E+6 psi
E=4E+6 psi
E=2E+6 psi
E=1E+6 psi
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Optimizing Proppant Selection
Too big or Too small?
Not strong enough?
More proppant?
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Impact of Primary Fracture Spacing
200 mD-ft primary frac and 2 mD-ft network,
100 ft network fracture spacing
Pressure (psi)
Pressure (psi) Pressure (psi)
Pressure (psi)
Pressure distribution after 3 months Pressure distribution after 1 yr
600 ft main fracture spacing
200 ft main fracture spacing
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Impact of Primary Fracture Spacing
100 ft network fracture spacing
Well AWell B
100 ft network fracture spacing
Well AWell B
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Impact of Network Fracture Spacing
200 mD-ft primary frac and 2 mD-ft network, 600 ft
primary fracture spacing
300 ft network fracture spacing
50 ft network fracture spacing
Pressure (psi)
Pressure (psi) Pressure (psi)
Pressure (psi)
Pressure distribution after 1 month Pressure distribution after 1 yr
600 ft
600 ft
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Impact of Network Fracture Spacing
2 mD-ft network fracture conductivity
Well AWell B
2 mD-ft network fracture conductivity
Well AWell B
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Impact of Network Fracture Spacing
2 mD-ft network fracture conductivity
Well AWell B
2 mD-ft network fracture conductivity
Well AWell B
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Impact of Matrix Permeability (1 x 10-5 mD)
2 mD-ft network fracture conductivity
50 ft spacing, k = 1 e-4 md
100 ft spacing, k = 1 e-4 md
50 ft spacing, k = 1 e-4 md
100 ft spacing, k = 1 e-4 md
Well A
Well B
50 ft spacing, k = 1 e-4 md
100 ft spacing, k = 1 e-4 md
50 ft spacing, k = 1 e-4 md
100 ft spacing, k = 1 e-4 md
Well A
Well B
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ConclusionsCharacterizing Fracture Growth leads to:
Better understanding well & fracture performanceMore reliable reservoir modeling and better reservoir
characterization
Resolution of created and effective fracture length
Better estimates ofIn situfracture conductivity
Improved completion & stimulation strategies
Stimulation fluid & proppant selection
Well placement and spacing
Number of stages (both vertical & horizontal wells)
Optimized designs (volume, rate)Optimum Fracture Treatment Designs and Field DevelopmentStrategies Tailored to Specific Geologic Environments
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Are we applying the right
combination of technologies?
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Fracture & Completion Strategy(horizontal gas wells, network fracture growth)
Conductivity of the primary fracture is likely acritical parameter (~50-100 mD-ft required)
Fracture complexity/network fracture spacing keyto well productivity and gas recovery
If network fracture spacing is on order 50 ft, then theeffect of matrix permeability on production issignificantly reduced
High relative conductivity primary fracture reducesthe impact of network fracture spacing
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Fracture & Completion Strategy(horizontal gas wells, network fracture growth)
Actual production profiles suggests that primary
fracture conductivity is low?
Understanding matrix permeability and un-propped
fracture conductivity is important when optimizing
treatment designs in unconventional gas reservoirs
Un-cemented horizontal completions, more difficult
to create a high relative conductivity primaryfracture?
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General Guidelines
In low modulus rock, it may not be possible toexploit complexity. (Haynesville?)
In reservoirs that areprone to fracture complexity,design goals should target:
Large networks for k~0.0001 md (E>4e6 psi) Supplemented with infinite conductivity primary fractures
Small networks for k~0.01 md (E>4e6 psi) Supplemented with infinite conductivity primary fractures
Simple fractures for k~1.0 md (E
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Strategy
Evaluate the impact of operational changes uponfracture complexity
o Low viscosity fluids generally promote fracturecomplexity and minimize damage
o High viscosity fluids reduce fracture complexity(Haynesville?)
o Pump rates, completion strategy, diversion, 100-mesh, etc.
Evaluate hybrid treatments to promote smallnetworks with infinite conductivity primaryfractures
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Strategy
Evaluate higher strength, smaller mesh, and lowerdensity propping agents that can significantlyimprove the conductivity of partially proppednetwork fractures
Deeper penetration, better proppant transport
Possibly enter and prop secondary networkfractures
Evaluate larger proppant volumesIncreased primary fracture conductivity
Increase network fracture conductivity
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Questions?
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Backup Slides
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Reservoir Simulation Study Goal: Evaluate the relationship between fracture complexity,
fracture conductivity, and proppant distribution on wellproductivity
Cases: Single fracture, complex planar growth, smallnetworks, and large networks
This presentation focuses on Small and Large Networks
Reservoirs: Gas with permeability of 0.0001, 0.01, and 1 md
Proppant distribution: Two limiting cases
Proppant is concentrated in a single primary fracture with infiniteconductivity (case 2)
Proppant is evenly distributed within the fracture network (cases1 & 3)
Evaluate the effect of network fracture conductivity on wellproductivity for the two limiting cases
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Example Fracture Treatments
Barnett Shale (SPE 95568)
k = 0.0001 mD (est.)
hf= 300 ft
xf= 1500 ft
xn = 2000 ft
xs = 50-300 ft (est.)
Treatment
60,000 bbl
385,000 lbsNote: Fracture dimensions and complexity from microseismic mapping
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Important Assumptions Cased and cemented wellbore
Primary fracture spacing controlled by distance betweenperforation clusters
Gas flow into wellbore at perforation clusters only
Fracture complexity (network fracture spacing) is notaffected by primary fracture spacing (distance betweenperforation clusters)
Pre-existing natural fracture system or rock fabric is presentand can be equally stimulated for the range of primaryfracture spacings evaluated
Network fracture conductivity is not affected by primaryfracture spacing
Stimulated Reservoir Volume (SRV) is equal for all cases(2000 x 106 ft3)
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Barnett Example
-1000
-500
0
500
1000
1500
2000
2500
3000
-1000 -500 0 500 1000 1500 2000 2500
West-East (ft)
South-North(ft)
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150 ft
150ft
2000
ft
Evenly Distributed
3000 ft
(Case 1)
150 ft
150ft
2000
ft
Evenly Distributed
3000 ft
(Case 1)
Proppant Distribution, 150 ft Network Fracture Spacing:
Barnett Shale Example (385,000 lbs prop)
0.015 lb/ft2
Note: Dimensions not to scale
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150 ft
150ft
2000
ft
Concentrated in a
dominant fracture
3000 ft
(Case 2)
150 ft
150ft
2000
ft
Concentrated in a
dominant fracture
3000 ft
(Case 2)
Proppant Distribution, 150 ft Network Fracture Spacing:
Barnett Shale Example (385,000 lbs prop)
0.43 lb/ft2
Note: Dimensions not to scale
P t Di t ib ti & N t k F t
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Proppant Distribution & Network Fracture
Growth Summary
If proppant is evenly distributed in network fractures,concentrations are probably too small to materiallyaffect conductivity
If proppant is concentrated in a primary fracture,concentrations mayprovide adequate conductivity fork
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Effect of Modulus & Stress on Embedment
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 2000 4000 6000 8000 10000 12000
Stress (psi)
Em
bedment(graindiameters
) 1E+6 psi
2E+6 psi
4E+6 psi
6E+6 psi
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Findings
Fracture complexity can be estimated byintegrating microseismic mapping, reservoir &
fracture modeling, core data, and well
performance
In some reservoirs, fracture complexity has been
shown to improve production. In other
reservoirs, complex growth has been shown to
damage productivity.
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Findings
If proppant is evenly distributed throughout large
fracture networks, the resulting concentrations
are inadequate to materially affect conductivity
To capitalize on the potential of unpropped and
partially propped regions, these networks should
be contacted by infinite conductivity primaryfractures