@wikipedia
Synonym: Pore Compressibility = Formation compressibilityCPHI
A measure of formation porosity
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c_r\phi = \frac{1}{\phi} \frac{\partial \phi}{\partial p} |
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There is a statistical correlation between initial formation compressibility
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Pore compressibility stays constant for small pressure variations but in a wide range of pressure variations the dependence on ambient pressure
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The typical values are:
cr ϕ = 0.5 ÷ 1.5 GPa-1
but may go higher for poorly consolidated rocks.
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In many practical cases the pore compressibility can be considered as poorly dependent on reservoir pressure variation:
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In this case porosity dependence on reservoir pressure can be simulated as:
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\phi(p) = \phi_i \cdot \left[ 1 + c_\phi \, (p-p_i) + 0.5 \, c^2_\phi \, (p-p_i)^2 \right] |
But in case the reservoir pressure is changing substantially one may need to account for the effect it takes on pore compressibility (see Pore compressibility @model).) and then reservoir pressure - porosity model is going to take the following form:
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\phi(p) = \phi_i \cdot \exp \left[ \int_{p_i}^p c_\phi\, dp \right] |
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics / Geomechanical Rock Modelling
[Compressibility][ initial pore compressibility ]
[ Pore compressibility @model ]
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