Correlation between pore compressibility $\begin{array}{l}c_r(p)\end{array}$ at a given pressure $\begin{array}{l}p\end{array}$ and initial pore compressibility $\begin{array}{l}c_{ri}\end{array}$ at initial formation pressure $\begin{array}{l}p_i\end{array}$ :

Correlation

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(1)	$\begin{array}{l}\displaystyle \displaystyle c_r(p) = c_{ri} \cdot \frac{ \ln \left( \frac{ p_n }{p_{\rm max}} \right) }{ \ln \left( \frac{p_{ni}}{p_{\rm max}} \right) }\end{array}$

(2)	$\begin{array}{l}\displaystyle p_n = p_{\rm min} + 1.75 \cdot \phi^{0.51} \cdot (p_{\rm max} - p)\end{array}$

(3)	$\begin{array}{l}\displaystyle p_{ni} = p_{\rm min} + 1.75 \cdot \phi^{0.51} \cdot (p_{\rm max} - p_i)\end{array}$

Wide pressure range: p_min = 1 MPa < p < p_max = 200 MPa

In many practical cases the pore compressibility can be considered as poorly dependent on reservoir pressure variation.

But in case the reservoir pressure is changing substantially one may need to account for the effect it takes on pore compressibility which can be fairly approximated by Dobrynin correlation (1).

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