A pore volume $\begin{array}{l}V_\phi\end{array}$ fraction of bulk rock volume $\begin{array}{l}V_r\end{array}$ containing the hydrodynamically connected fluids (also called free fluids) within each pore element:

$\begin{array}{l}\displaystyle \phi_e = \frac{V_\phi}{V_r}\end{array}$

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 porosity $\begin{array}{l}\phi_{\rm opn}\end{array}$ and closed porosity $\begin{array}{l}\phi_{\rm cls}\end{array}$ :

$\begin{array}{l}\displaystyle \phi_e = \phi_{\rm opn} + \phi_{\rm cls}\end{array}$

The log name is PHIE.

Effective porosity is a function of reservoir pressure at a given location $\begin{array}{l}p({\bf r})\end{array}$

(1)	$\begin{array}{l}\displaystyle \phi(\mathbf{r}, \ p) = \phi_0(\mathbf{r}) \exp \left[ - \int_{p_i}^p c_r(p) \, dp \right]\end{array}$

where

$\begin{array}{l}c_r(p)\end{array}$	pore compressibility
$\begin{array}{l}p_i\end{array}$	initial formation pressure

Page tree

See also

Page tree

Effective porosity (PHIE)

See also