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A pore volume
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:open
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subject to conditione, c}:
LaTeX Math Block |
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\phi_e = \phi_{e,\rm oopn} + \phi_{e,\rm ccls} |
The log name is PHIE.
Effective porosity is a function of reservoir pressure at a given location
: LaTeX Math Block |
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\phi_e(\mathbf{r}, \ p) = \phi_0{ei}(\mathbf{r}) \exp \left[ - \int_{p_i}^p c_r\phi(p) \, dp \right] |
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:
LaTeX Math Block |
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\phi_e(\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 ] [ Open Connected pore volume ] [ Closed pore volume ] [ Porosity ] [ Open porosity ] [ Closed porosity ][ Initial Porosity ϕi ]
[ Pore compressibility @model ]