Roach plot for abnormally pressured gas reservoirs

Input(s)

$p_{i} / Z_{i}$: Initial $\mathrm{P} / \mathrm{z}$ Ratio (psi)

$c_{t}$: Rock Compressibility (1/psi)

$G_{p}$: Gas Produced (SCF)

$G$: Gas in Place (SCF)

Output(s)

$\frac{p}{Z}$: Current $\mathrm{P} / \mathrm{z}$ Ratio (psi)

Formula(s)

$$ \frac{p}{Z}=\left(\frac{p_{i}}{Z_{i} * c_{t}}\right) *\left(1-\left(\frac{G_{p}}{G}\right)\right) $$

Reference(s)

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