In many practical cases the pore compressibility can be considered as independent on reservoir pressure variation: $\begin{array}{l}c_\phi(p) = c_r\phi= \rm const\end{array}$ .

But in case the reservoir pressure is changing substantially one may need to account for the effect it takes on pore compressibility.

The model usually relates pore compressibility $\begin{array}{l}c_\phi(p)\end{array}$ to a given pressure $\begin{array}{l}p\end{array}$ and initial pore compressibility $\begin{array}{l}c_{\phi i}\end{array}$ at initial formation pressure $\begin{array}{l}p_i\end{array}$ .

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

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

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

Dobrynin

Sandstone

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

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Pore compressibility pressure @model

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