Using Induced Seismicity Using Induced Seismicity to Predict and Monitorto Predict and MonitorReservoir Permeability Reservoir Permeability

PathwaysPathways

Using Induced Seismicity Using Induced Seismicity to Predict and Monitorto Predict and MonitorReservoir Permeability Reservoir Permeability

PathwaysPathways

STRM LLC

Positive Rate Correlationsfor Field Study A

Flood Directionalities> 40 Fields

Shmax

Rate Correlation Statistics (Heffer et al., 1997)

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s Crust

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s Crust

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s Crust

Rate Correlation Statistics (Heffer et al., 1997)

5 kms

None or negative change in productionProduction increase

Positive correlations have “zero lag time” at all distances.

Shmax

Shmax

Injection well

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s Crust

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s 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.

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s 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.

Critical Observations on the Behavior Critical Observations on the Behavior of Fluid Systems in the Earth’s Crustof Fluid Systems in the Earth’s Crust

12

Pf in a well stress state about well.

2) stress state failure of the medium on critically oriented cracks seismicity.

3) Permeable cracks = critically oriented cracks.

4) Seismicity induced by Pf = permeable crack

system = Permeability (P) seismicity.

The STRM ModelThe STRM Model

Observation: The state of stress in earth’s

brittle crust is everywhere near failure.

STRM HypothesisSTRM Hypothesis

P Seismicity SignatureSpatial: Given a mechanically isotropic mediumwith 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.

Test of HypothesisTest of Hypothesis Data from Rangely Field Experiment, Colorado Data from Rangely Field Experiment, Colorado

•Observations: Monitoring microseismicity and fluid pressure during a water flood.– Rapid response at distance: Earthquake activity

up to > 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.

Pattern of Seismicity Pattern of Seismicity (Map View)(Map View)

Data from Rangely Field Experiment, Colorado Data from Rangely Field Experiment, Colorado

10/69 - 10/70 11/70 - 7/71 8/71 - 10/71

11/71 - 8/72 9/72 - 5/73 6/73 - 5/74

1 Km

Injection Withdrawal Injection

Injection Injection Shut in

Fluid PressureIsobars

Injection Wells

Seismicity

Shmax

70

140

210

280

N

255

Eq Magnitude -0.5Raleigh et al, 1976

Pattern of Seismicity Pattern of Seismicity (Section (Section View)View)

Data from Rangely Field Experiment, Colorado Data from Rangely Field Experiment, Colorado

Seismicity Boundary

1

1

1

1

Raleigh et al, 1976

Brittle Failure Processes of the Brittle Failure Processes of the Earths CrustEarths Crust

• Macro-Seismicity, Micro-seismicity and Creep

10-510-6 10-4 10-3 10-2 10-1 100 101 102 103

Approximate Rupture size - meters

Creep Macro-Seismicity

Micro-Seismicity

Imagin

g M

eth

od

Earthquake Seismology

Seismic Structure Tomography

SST

Passive Seismic Emission Tomography

PSET

Earthquake Magnitude

Passive Seismic Emission Tomography Passive Seismic Emission Tomography (PSET(PSET™)™)

t2

t1

ti

t3

Micro-Array

Given: Velocity Model

Passive Seismic Emission Tomography Passive Seismic Emission Tomography (PSET(PSET™)™)

Slice through PSET cube.

Hot colors = emax

Brittle Failure Processes of the Brittle Failure Processes of the Earths CrustEarths Crust

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

Clast scale Deformation

Grain scale Deformation

Bed scale Deformation

Heterogeneity of Brittle Failure Heterogeneity of Brittle Failure Processes of the Earths CrustProcesses of the Earths Crust

Valley and Ridge: Virginia

2 Km

Heterogeneity of Brittle Failure Heterogeneity of Brittle Failure Processes of the Earths CrustProcesses of the Earths Crust

Bear Valley: Pa.

Heterogeneity of Brittle Failure Heterogeneity of Brittle Failure Processes of the Earths CrustProcesses of the Earths Crust

North West Territory: Canada

1 Km