# Annular capacity between casing and multiple strings of tubing

## Input(s)

\(\mathrm{D}_{\mathrm{i}}\): Inner Diameter of Casing (in.)

\(\mathrm{T}_{1}\): Diameter of Tubing 1 (in.)

\(\mathrm{T}_{2}\): Diameter of Tubing 2 (in.)

## Output(s)

\(\mathrm{C}_{\mathrm{a}}\): Annular Capacity \((\mathrm{gal} / \mathrm{ft})\)

## Formula(s)

\[
\mathrm{C}_{\mathrm{a}}=\frac{\mathrm{D}_{\mathrm{i}}^{2}-\left(\mathrm{T}_{1}^{2}+\mathrm{T}_{2}^{2}\right)}{1029.4}
\]

## Reference(s)

Lyons, W. C., Carter, T., and Lapeyrouse, N. J., 2012, Formulas and Calculations for Drilling, Production and Workover, Third Edition, Gulf Professional Publishing, Page: 15.