Fraction of the total solution gas retained in the reservoir as free gas

Input(s)

$\mathrm{N}$: Oil in Place $(\mathrm{STB})$

$\mathrm{R}_{\mathrm{p}}$: Produced Gas-Oil Ratio (SCF/STB)

$\mathrm{N}_{\mathrm{p}}$: Cumulative Oil Production (STB)

$\mathrm{R}_{\mathrm{si}}$: Initial Gas Solubility $(\mathrm{SCF} / \mathrm{STB})$

$\mathrm{R}_{\mathrm{s}}$: Gas Solubility $(\mathrm{SCF} / \mathrm{STB})$

Output(s)

$\alpha_{\mathrm{g}}$: Retained Gas Volume of the Total Gas (fraction)

Formula(s)

$$ \alpha_{\mathrm{g}}=1-\left(\frac{\mathrm{N}_{\mathrm{p}} * \mathrm{R}_{\mathrm{p}}}{\mathrm{N} * \mathrm{R}_{\mathrm{si}}-\left(\mathrm{N}-\mathrm{N}_{\mathrm{p}}\right) * \mathrm{R}_{\mathrm{s}}}\right) $$

Reference(s)

Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 4, Page: 314.