# Time to reach the semi-steady state for a gas well in a circular or square drainage area (2)

## Input(s)

\(\mu_{g i}\): Initial Gas Viscosity \((\mathrm{cP})\)

\(\emptyset\): Porosity (fraction)

A: Drainage Area \(\left(\mathrm{ft}^{2}\right)\)

\(\mathrm{k}\): Effective Gas Permeability \((\mathrm{mD})\)

\(c_{t i}\): Initial Total Compressibility \((1 / \mathrm{psi})\)

## Output(s)

\(t_{p s s}\): Time (h)

## Formula(s)

\[
t_{p s s}=\frac{15.8 \phi * \mu_{g i} * c_{t i} * A}{k}
\]

## Reference(s)

Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3, Page: 194.