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.