Level 3 PreFlow State Map View

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Using Induced Seismicity to Predict and
MonitorReservoir Permeability Pathways
2
Critical Observations on the Behavior of Fluid
Systems in the Earths Crust
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Critical Observations on the Behavior of Fluid
Systems in the Earths Crust
Injection well
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Critical Observations on the Behavior of Fluid
Systems in the Earths Crust
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Critical Observations on the Behavior of Fluid
Systems in the Earths Crust
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Critical Observations on the Behavior of Fluid
Systems in the Earths Crust

• Hydraulically conductive fractures form the
  permeability system and are critically stressed
  according to Mohr-Coulomb behavior.
• Hydraulically conductive fractures show a
  conoidal distribution with respect to Shmax .
• Critically stressed fractures containing fluid
  are the weakest part of the naturally occurring
  fracture system and will respond first to a
  change in stress state.

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Critical Observations on the Behavior of Fluid
Systems in the Earths Crust

• Micro-seismicity and creep created by a change in
  stress state will occur dominantly and in many
  cases exclusively on fractures forming the
  permeability system.

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8
The STRM Model
Observation The state of stress in earths
brittle crust is everywhere near failure.

• 1) D Pf in a well ? D stress state about well.
• 2) D stress state ? failure of the medium on
  critically oriented cracks ? seismicity.
• 3) Permeable cracks critically oriented
  cracks.
• 4) Seismicity induced by DPf permeable crack
• system Permeability (P) seismicity.

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STRM Hypothesis

• P Seismicity Signature
• Spatial Given a mechanically isotropic medium
• with an isotropic crack distribution.
• Should occupy opposing conoidal volumes.
• Cone axis should Shmax of ambient stress field.
• Apical angles should range from 60o - 90o.
• Seismicity should extend for kms from injection
  point.
• Temporal
• Seismicity should propagate from injection point
  at rates ? km/month.

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Test of Hypothesis Data from Rangely Field
Experiment, Colorado

• Observations Monitoring microseismicity and
  fluid pressure during a water flood.
• Rapid response at distance Earthquake activity
  up to gt 4 km from injectors ceases within 1 day
  of shut in.
• Increase in Pf ? Increase in earthquake activity.

• Spatial and temporal characteristics of
  microseismicity consistent with STRM hypothesis.

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Pattern of Seismicity (Map View) Data from
Rangely Field Experiment, Colorado
Raleigh et al, 1976
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Pattern of Seismicity (Section View) Data from
Rangely Field Experiment, Colorado
Raleigh et al, 1976
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Brittle Failure Processes of the Earths Crust

• Macro-Seismicity, Micro-seismicity and Creep

Approximate Rupture size - meters
10-5
10-6
10-4
10-3
10-2
10-1
100
101
102
103
Macro-Seismicity
Micro-Seismicity
Creep
Imaging Method
Earthquake Magnitude
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Passive Seismic Emission Tomography (PSET)
t1
Micro-Array
t2
t3
Sti
Given Velocity Model
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Passive Seismic Emission Tomography (PSET)
Slice through PSET cube. Hot colors emax
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Brittle Failure Processes of the Earths Crust

• Failure processes in the brittle (seismogenic)
  crust the role of fracturing in creep.

Clast scale Deformation
Grain scale Deformation
Bed scale Deformation
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Heterogeneity of Brittle Failure Processes of the
Earths Crust
Valley and Ridge Virginia
2 Km
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Heterogeneity of Brittle Failure Processes of the
Earths Crust
Bear Valley Pa.
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Heterogeneity of Brittle Failure Processes of the
Earths Crust
North West Territory Canada
1 Km