Compressibility (porous reservoir)

@wikipedia

A measure of formation porosity  $//<![CDATA[ \begin{array}{l}\phi\end{array} //]]>$ change due to pressure  $//<![CDATA[ \begin{array}{l}p\end{array} //]]>$ variation:

It stays constant for small pressure variations ( $//<![CDATA[ \begin{array}{l}c_r(p) = \rm const\end{array} //]]>$) but for a wide range pressure variations the dependence on ambient pressure  $//<![CDATA[ \begin{array}{l}c_r(p)\end{array} //]]>$ can not be neglected and can be estimated experimentally or via popular compressibility-porosity correlations on $//<![CDATA[ \begin{array}{l}c_r(\phi)\end{array} //]]>$. 

The typical values are in  $//<![CDATA[ \begin{array}{l}0.5 \div 1.5 \cdot 10^{-6} \, {\rm kPa}^{-1}\end{array} //]]>$ but may go higher for poorly consolidated rocks.