Transcript Level 3 Pre-Flow State – Map View

Using Induced Seismicity
to Predict and Monitor
Reservoir Permeability
Pathways
STRM LLC
Critical Observations on the Behavior
of Fluid Systems in the Earth’s Crust
Shmax
Positive Rate Correlations
for Field Study A
Rate Correlation Statistics (Heffer et al., 1997)
Flood Directionalities
> 40 Fields
Critical Observations on the Behavior
of Fluid Systems in the Earth’s Crust
Shmax
5 kms
Injection well
Shmax
None or negative change in production
Production increase
Positive correlations have “zero lag time”
at all distances.
Rate Correlation Statistics (Heffer et al., 1997)
Critical Observations on the Behavior
of Fluid Systems in the Earth’s Crust
Critical Observations on the Behavior
of Fluid Systems in the Earth’s Crust
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 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
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.
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The STRM Model
Observation: The state of stress in earth’s
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.
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.
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
Injection
Injection Wells
Fluid Pressure
Isobars
Withdrawal
Injection
1 Km
10/69 - 10/70
11/70 - 7/71
Injection
Injection
8/71 - 10/71
70
140
Shut in
210
255
280
Seismicity
Shmax
11/71 - 8/72
Raleigh et al, 1976
9/72 - 5/73
Eq Magnitude  -0.5
6/73 - 5/74
N
Pattern of Seismicity
(Section View)
Data from Rangely Field Experiment, Colorado
s1
s1
Seismicity
Boundary
s1
s1
Raleigh et al, 1976
Brittle Failure Processes of the
Earths Crust
• Macro-Seismicity, Micro-seismicity and Creep
Approximate Rupture size - meters
10-6
10-5
10-4
10-3
10-2
10-1
Imaging Method
Creep
100
101
102
MicroSeismicity
Passive Seismic
Emission Tomography
PSET
103
MacroSeismicity
Earthquake Seismology
Seismic Structure
Tomography
SST
Earthquake Magnitude
Passive Seismic Emission
Tomography (PSET™)
t1
Micro-Array
t2
t3
Sti
Given: Velocity Model
Passive Seismic Emission
Tomography (PSET™)
Slice through PSET
cube.
Hot colors = emax
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