Remaining gas in place in coalbed methane reservoirs

Input(s)

A: Drainage Area (acres)

Ø: Porosity (fraction)

\(\mathrm{h}\): Thickness (ft)

\(\mathrm{B}_{\mathrm{w}}\): Water Formation Volume Factor (bbl/STB)

\(\mathrm{W}_{\mathrm{p}}\): Cumulative Water Produced (bbl)

\(\mathrm{S}_{\mathrm{wi}}\): Water Saturation (fraction)

\(\mathrm{P}_{\mathrm{i}}\): Initial Pressure \((\mathrm{psi})\)

P: Current Reservoir Pressure (psi)

\(\mathrm{c}_{\mathrm{f}}\): Formation Compressibility \((1 / \mathrm{psi})\)

\(\mathrm{c}_{\mathrm{w}}\): Water Compressibility (1/psi)

\(\mathrm{E}_{\mathrm{g}}\): Gas Expansion Factor \((\mathrm{SCF} / \mathrm{bbl})\)

Output(s)

\(\mathrm{G}_{\mathrm{R}}\): Remaining Gas at Reservoir Pressure (SCF)

Formula(s)

Reference(s)

Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 3, Page: 227.