Microseismic Monitoring and Geomechanical Modelling of CO2 - bris

CHAPTER 6.
GENERATING ANISOTROPIC SEISMIC MODELS BASED ON GEOMECHANICAL SIMULATION
Define S r (from EBSD or high pressure behaviour)
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For each velocity measurement at specified pressure:
Define C obs from velocities
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Loop over B N /B T values
Initialise crack density tensor
α kk = 0
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Loop over number of iterations
Define C model = f(S r , α kk , B N /B T )
(equations 6.22 – 6.24)
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Define model misfit:
δb = C obs − C model
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Define Jacobean: J = δC
δα
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Invert δb = Jδm
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Update model: α kk = α kk + δm
End iteration loop
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Back calculate velocities using final value of C model
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Compute misfit between modelled and observed velocities
δV = (V obs −V model ) 2
V obs
End B N /B T grid-search
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Select the value of B N /B T that minimises δV
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Select the values of α kk computed with this B N /B T value
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Move on to next pressure measurement
Figure 6.3: Workflow for inverting velocity measurements for B N /B T and the crack density tensor.
Modified from Hall et al. (2008).
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