hydraulic fracturing design for optimum well productivity frank e. syfan, jr., pe, spee syfan...
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Hydraulic Fracturing Design for Optimum Well Productivity
Frank E. Syfan, Jr., PE, SPEE
Syfan Engineering, LLC
February 26, 2015
S
Outline
Critical Fracture Design Parameters Rock Mechanics Fracture Mechanics Fluid Systems Proppant Selection
Case Histories: Case A: Marcellus Shale Case B: Eagle Ford Shale Case C: Bakken Case D: Cotton Valley
Summary Conclusions
2
3
Critical Fracture ParametersRock Mechanics
Mineralogy Content: Quartz, calcite, clay (??) Shales: Many are not in strictest geological sense!
Poisson’s Ratio
Modulus of Elasticity (Young’s Modulus)
In-Situ Stress
4
Fracture Face Skin
Choked Fracture Skin
Half-Length & Width What is optimum length? Perkins & Kern (1961)
Fracture Conductivity!!! wkf
CfD
Critical Fracture ParametersFracture Mechanics
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Fluid & Additive Design Slickwater DOESN’T Work Everywhere! Chemical and Fluid Compatibility Gel Stability and Breaker Tests Temperature Ranges Nano-Fluid Non-Emulsifiers Polyacrylamide Breakers ISO 13503-1, 13503-3, 13503-4
Critical Fracture ParametersFluid Systems
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Critical Fracture ParametersProppant Selection
a-Qtz
Ceramic
ResinCoated
7
Incr. Cost & Performance
13+12
8
54
0
Intermediate
Premium
Economy
Intermediate
Bauxite
Incr
. Clo
sure
Pre
ssur
e, K
psi
RC Ceramics
RC a-Qtz
Ceramics
a-Qtz
LWC
Critical Fracture ParametersProppant Selection
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The Ideal Proppant Crush resistance / high strength Slightly deformable, not brittle No embedment Low specific gravity Chemical resistance No flowback Complete system compatibility Ready availability Cost effective
Reality: The Ideal Proppant Doesn’t Exist!!
Critical Fracture ParametersProppant Selection
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Infinite vs. Finite Conductivity Formation Permeability Depth/Closure Stress Formation Ductility/Embedment
What is Brinell Hardness?
Critical Fracture ParametersProppant Selection
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Median Particle Diameter Cyclic Stress Multi-Phase Flow Proppant Flowback Non-Darcy Effects
Beta Factor
Critical Fracture ParametersProppant Selection
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Fracture Conductivity – Wkf
Single Most Important Factor to Achieve! Dimensionless Conductivity
Fracture Flow Capacity Divided by Reservoir Flow Capacity.
Considered “Infinite” the fracture deliverability exceeds reservoir deliverability with negligible pressure loss.
Critical Fracture ParametersConductivity
f
fffD xk
wkC
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Critical Fracture ParametersConductivity: McGuire & Sikora (1960)
Dimensionless Productivity Index vs. Dimensionless
Conductivity (Square Reservoir)
Dimensionless Productivity Index vs. Dimensionless
Conductivity (Rectangular Reservoir – 1/10)
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Critical Fracture ParametersFines
12/20 Hickory/Brady – 6,000 psi
Intermediate Strength Ceramic – 8,000 psi
RC Proppant – 8,000 psi
StimLab Proppant Consortium, 1997 – 2006
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Brown vs. Northern White? API 19C (ISO 13503-2) Guidelines Are Specific!!
Sieve Distribution Krumbein Factors Turbidity Acid Solubility
K-Value (Also Called Crush Resistance) Point Where Fines >10.0% Relative Number Only!!
Critical Fracture ParametersDepth/Closure Stress
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SPE 84304 (2003) Particle Sieve Distribution Variations
Field Samples – 20/40 N. White @ 25X
0.545 mm
0.703 mm
Courtesy: PropTester – Houston TX
Critical Fracture ParametersMedian Particle Diameter
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Critical Fracture ParametersMedian Particle Diameter
Courtesy: PropTester – Houston TX
0
5
10
15
20
25
30
35
40
45
16 20 25 30 35 40 50 PAN
Sieve Size
% P
art
icle
Dis
trib
uti
on
Public Domain Job Sample
Flow Capacity Decreases
MPD = 0.543 mm
MPD = 0.710 mm
Each Proppant Sample Passes ISO 13503-2 Guidelines!
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Critical Fracture ParametersMedian Particle Diameter
Courtesy: PropTester – Houston TX
Co
nd
uc
tiv
ity
(m
d-f
t)
100
1,000
10,000
2,000 4,000 6,000 8,000 10,000
Closure Stress (psi)
Published Data
MPD = 0.710 mm
Actual Data
MPD = 0.543 mm
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A Quantity Relating Pressure Loss In The Fracture to Liquid or Gas Production Rates (velocities).
Governed by Forchheimer’s Equation Darcy Effects Non-Darcy Effects
• Inertial Effect• 2 - Dominate!• PSD Effects Beta
Critical Fracture ParametersBeta Factor
2.fluidfluid
frac
fluidfluid
frac
frac vk
v
X
P
Outline
Critical Fracture Design Parameters Rock Mechanics Fracture Mechanics Fluid Systems Proppant Selection
Case Histories: Case A: Marcellus Shale Case B: Eagle Ford Shale Case C: Bakken Case D: Cotton Valley
Summary Conclusions
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Case History A: Marcellus Shale
Reservoir & Fracture Parameters
Description Value
Reservoir Depth, ft 7.876
Reservoir Thickness, ft 162
Hydrocarbon Porosity, % 4.2
Pore Pressure, psi 4.726
Temperature, oF 175
Drainage Area, ac 80
Aspect Ratio (xe/ye) ¼
BHFP, psi 1,450 – 530
Lateral Length, ft 2,100
Number of Stages 7
Clusters per Stage 5
Fracture & Reservoir Match
Description Value
Reservoir Permeability, nD 583.0
Permeability-Thickness, md-ft 0.094
Propped Length, ft 320
Fracture Conductivity, md-ft 3.77
Dimensionless Conductivity 20.2
Choked Skin, dim +0.096
Equivalent Fractures 6
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Case History A: Marcellus Shale
Predicted Gas Production Rate Predicted Cum. Gas Production
SPE 166107
Case History A: Marcellus Shale
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Case History B: Eagle Ford Shale
Reservoir & Fracture Parameters
Description Value
Reservoir Depth, ft 10,875
Reservoir Thickness, ft 283
Hydrocarbon Porosity, % 5.76
Pore Pressure, psi 8,350
Temperature, oF 285
Drainage Area, ac 80
Aspect Ratio (xe/ye) ¼
BHFP, psi 3,900 – 1,500
Lateral Length, ft 4,000
Number of Stages 10
Clusters per Stage 4
Fracture & Reservoir Match
Description Value
Permeability-Thickness, md-ft 0.0049
Propped Length, ft 131
Fracture Conductivity, md-ft 0.86
Dimensionless Conductivity 382
Choked Skin, dim +0.0254
Equivalent Fractures 40
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Case History B: Eagle Ford Shale
Predicted Gas Production Rate Predicted Cum. Gas Production
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Case History C: Bakken Shale
Reservoir & Fracture Parameters
Description Value Description Value
Reservoir Depth, ft 9,881 Drainage Area, ac 640
Reservoir Thickness, ft 46 BHFP, psi 1,500
Rsvr. Permeability, mD 0.002 Effective Frac. Length, ft 420
Porosity, % 5.0 Frac. Conductivity, md-ft 200
Pore Pressure, psi 4,900 Dimensionless Conductivity 238
Temperature, oF 209 Lateral Length, ft 5,000
Rsvr. Compressibility, 1/psi 2.0 E-05 Transverse Fractures 12
Rsvr. Viscosity, cP 0.30
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Case History C: Bakken Shale
Predicted Oil Production Rate Predicted Cum. Oil Production
26SPE 166107
Case History D: E. TX Cotton Valley
Description Value Description Value
Reservoir Depth, ft 9,000 BHFP, psi 1,500
Reservoir Thickness, ft 100 Effective Frac. Length, ft 1,500
Rsvr. Permeability, mD 0.001 Frac. Conductivity, md-ft 114
Porosity, % 7.0 Dimensionless Conductivity 76
Pore Pressure, psi 6,000 Lateral Length, ft 2,000
Temperature, oF 285 Transverse Fractures 7
Drainage Area, ac 640
Reservoir & Fracture Parameters
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Case History D: E. TX Cotton Valley
Predicted Gas Production Rate Predicted Cum. Gas Production
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Outline
Critical Fracture Design Parameters Rock Mechanics Fracture Mechanics Fluid Systems Proppant Selection
Case Histories: Case A: Marcellus Shale Case B: Eagle Ford Shale Case C: Bakken Case D: Cotton Valley
Summary Conclusions
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Summary
Proper fracture design and ultimately, fracture optimization, cannot and will not happen without sound engineering practices!
Without sound engineering, initial production rates, ultimate recovery, NPV, and rate-of-return will be compromised.
At the End of the Day……
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Conclusions
Understanding the rock mechanics is essential to consistently achieving high conductivity fractures.
McGuire and Sikora (1960) holds true regardless of reservoir type and ultimately dictates reservoir and production performance.
Fracture conductivity and dimensionless fracture conductivity ultimately govern the initial production rates and ultimate recoveries regardless of the type of reservoir lithology.
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Conclusions
Case A (Marcellus Shale) and Case B (Eagle Ford Shale) matches, illustrate the importance of achieving high conductivity transverse fractures in a horizontal wellbores.
Increasing fracture conductivity, regardless of reservoir type, results in a significant positive impact on ROR and NPV.
SPE 166107 32
THANK YOU FOR YOUR TIME AND TO THE FORT WORTH SPE
SECTION FOR INVITING ME TO MAKE THIS PRESENTATION.
QUESTIONS??
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