@wikipedia
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A pore volume
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fraction of bulk rock volume containing the hydrodynamically connected fluids (also called free fluids) within each pore element:| LaTeX Math Block |
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\phi_e = \frac{V_\phi}{V_r} |
The log name is PHIE.
The reason to introduce this concept is that a part of the actual inter-grain void is filled with shale thus reducing the actual volume available for fluids.
It splits into two components:
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subject to condition:
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| Omega_R |
\ Omegaphi_ Re = \ Omega_ephi_{\rm opn} + \Omegaphi_{sh} + \Omega_mThe usual practice is to use relative volumes\rm cls} |
Effective porosity is a function of reservoir pressure at a given location
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| Omega_R |
\phi_e(\mathbf{r}, \ p) = \frac{\Omega_e}{\Omega_R}, \quad V_{sh} = \frac{\Omega_{sh}}{\Omega_R}, \quad V_m = \frac{\Omega_m}{\Omega_R}which are measured in V/V units (or fracs) and honor the following constraint: | LaTeX Math Block |
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| anchor | V_Rphi_{ei}(\mathbf{r}) \exp \left[ \int_{p_i}^p c_\phi(p) \, dp \right]
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where
This leads to the effect of Porosity Shrinkage.
Since the pore compressibility is very low (~ cϕ = 0.5 ÷ 1.5 GPa-1) and has a weak dependence on reservoir pressure for subsurface rocks in petroleum reservoirs the | LaTeX Math Block Reference |
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can be written as:
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\phi_e +V_{sh} + V_m = 1| Anchor |
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| phie | phie | The relative effective pore volume
contains free or connate fluids (water, oil , gas) and called effective porosity.It corresponds to the air porosity of the dried laboratory cores: | LaTeX Math Inline |
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| body | \phi_e = V_{\rm air \, core} |
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. (\mathbf{r}, \ p) = \phi_{ei}(\mathbf{r}) \cdot \left[ 1 + c_\phi \, (p-p_i) + 0.5 \, c_\phi^2 \, (p-p_i)^2 \right]
Most Subsurface E&P Disciplines (except Petrophysics) usually omit index "e" and denote Effective porosity as .
See also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics (PP) / Volumetric Rock Model
[ Basic reservoir properties ] [ Pore volume ] [ Connected pore volume ] [ Closed pore volume ] [ Porosity ] [ Open porosity ] [ Closed porosity ][ Initial Porosity ϕi ]
[ Pore compressibility @model ]
