Using Induced Seismicity to Predict and Monitor Reservoir Permeability Pathways STRM LLC

Positive Rate Correlations for Field Study A Flood Directionalities > 40 Fields Sh max Rate Correlation Statistics (Heffer et al., 1997) Critical Observations on the Behavior of Fluid Systems in the Earth’s Crust

Rate Correlation Statistics (Heffer et al., 1997) 5 kms None or negative change in production Production increase Positive correlations have “zero lag time” at all distances. Sh max Injection well

Critical Observations on the Behavior of 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 Sh max. 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 of 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 of Fluid Systems in the Earth’s Crust 12

 P f 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  P f = permeable crack system = Permeability (P) seismicity. The STRM Model Observation: The state of stress in earth’s brittle crust is everywhere near failure.

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

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 > 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 (Map View) Data from Rangely Field Experiment, Colorado Raleigh et al, 1976

Pattern of Seismicity (Section View) Data from Rangely Field Experiment, Colorado Seismicity Boundary 11 11 11 11 Raleigh et al, 1976

Brittle Failure Processes of the Earths Crust Macro-Seismicity, Micro-seismicity and Creep Approximate Rupture size - meters Creep Macro- Seismicity Micro- Seismicity Imaging Method Earthquake Seismology Seismic Structure Tomography SST Passive Seismic Emission Tomography PSET Earthquake Magnitude

Passive Seismic Emission Tomography (PSET™) t2 t1  ti t3 Micro-Array Given: Velocity Model

Passive Seismic Emission Tomography (PSET™) Slice through PSET cube. Hot colors = e max

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

Heterogeneity of Brittle Failure Processes of the Earths Crust Valley and Ridge: Virginia 2 Km

Heterogeneity of Brittle Failure Processes of the Earths Crust Bear Valley: Pa.

Heterogeneity of Brittle Failure Processes of the Earths Crust North West Territory: Canada 1 Km