What Do Hydraulic Fractures May Look Like? · Suarez-Rivera et al., ARMA 2013 Hydraulic Fracturing...
Transcript of What Do Hydraulic Fractures May Look Like? · Suarez-Rivera et al., ARMA 2013 Hydraulic Fracturing...
What Do Hydraulic Fractures May Look Like?
Roberto Suarez-Rivera
W.D Von Gonten Co and W.D Von Gonten Laboratory
Vaca Muerta shaleOutcrop
Montney shaleOutcrop
Understanding the RockRock Fabric and Heterogeneity
WolfcampCore
WolfcampCore
SEM
SEM
Layered Heterogeneity (Eagleford Example)
Layered Heterogeneity (Wolfcamp Example)
Layering and Fracture Toughness
Hard(High Modulus) material
Hard/SoftCouplets
The layered rock is 40% tougher than the homogeneous rock
sh
sh
sv
sv
Rock Layering and Hydraulic Fracturing
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Layered Rock (High Resolution Logging) Layered Rock HF Model
Consequences of Layering and Weak Interfaces
Stress Concentrators(simulated perforations)
Fracture Toughness Testing under Stress
Rock has preferential directions of failure (i.e., weak interfaces)
Fracture orientation is controlled by the rock fabric
Suarez-Rivera et al., ARMA 2013 Hydraulic Fracturing Workshop.
Consequences of Layering and Weak Interfaces
Layered Niobrara shaleSuarez-Rivera et al., ARMA 2013 Hydraulic Fracturing Workshop.
Fracturing in Layered RocksConsequences of Layering and Interfaces
Propped horizontal fracture in Eagleford vertical pilot well with core
Suarez-Rivera et al., 2016 URTEC.
Core Drilling Induced Fractures
Soft layer
Hard layer
Soft layer
Actual Wellbore Fracture
Fracturing in Layered Rocks
Rock Layers, Weak Interfaces and Fracture Step-
Overs
Conceptual Model
Weak
Weak
ConductivityConductivity
• Thick Reservoir• Fracture Containment within Flow Unit• Multiple Conductivity Pinch Points• Poor Producer
• Thin Reservoir• Fracture Containment within Flow Unit• No Conductivity Pinch Points• Better Producer
Field Evidence Using Pre and Post Dipole Sonic MeasurementsLoss of Connectivity to the Wellbore During Drawdown
(The SRV Shrinks)
Suarez-Rivera et al., 2016 URTEC.
Layering and Fracture Height Growth
16 m
Pf
s11
Loss of Connectivity to the Wellbore During Drawdown
Rockfield (2D TGR) Software
Effective FractureHeight
Stress Controls on Hydraulic Fracture Propagation
Homogeneous Layered Layered and Fractured
sv
pp
Stre
ss
dif
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Normal Overpressure Highly Overpressure
0.8 – 0.9 psi/ft
0.5 – 0.7 psi/ft
Competition betweenstrength anisotropy and stress anisotropy
Operational Controls for Hydraulic Fracture Propagation
10 fracture stage20 ft spacing200 ft stage length~300 ft fracture half length
Strong differences in geometry are observed between fracture regimes, even for homogeneous materials
E.V. Dontsov, T. Picha, Suarez-Rivera (in progress).
Look for the following:
Rock fabric (Strength anisotropy): Layering and interfaces, including natural fractures and their frequency
Stress anisotropy: High pore pressure, typically means low effective stress and low stress anisotropy
Operational controls: How is the fracture energy dissipated? Viscosity dominated or toughness dominated
Near wellbore effects: Unfortunately the initial fracture geometry has long term consequences on the overall fracture. How we initiate fractures matters.
Drawdown: When the fracture geometry is complex the potential for fracture segmentation is high, and the SRV shrinks as a function of time during drawdown.
Summary: What do Hydraulic Fractures May Look Like Downhole
Thank You