Rock expansion term in abnormally pressured gas reservoirs

Input(s)

$c_{f}$: Formation Compressibility $(1 / \mathrm{psi})$

$c_{w}$: Water Compressibility $(1 / \mathrm{psi})$

$S_{w i}$: Initial Water Saturation (fraction)

Output(s)

$E_{R}$: Rock Expansion Term (1/psi)

Formula(s)

$$ E_{R}=\frac{c_{f}+c_{w} * S_{w i}}{1-S_{w i}} $$

Reference(s)

Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3, Page: 213