Free Gas in Place

Free Gas in Place Formula
\( G_f \;=\;  7758 \; A \; h \; n \; ( 1 - S_{wi} ) \; E_{gi} \)     (Free Gas in Place) \( A  \;=\;  G_f  \;/\;  7758 \; h \; n \; ( 1 - S_{wi} ) \; E_{gi} \) \( h \;=\;  G_f  \;/\;  7758 \; A \; n \; ( 1 - S_{wi} ) \; E_{gi} \) \( n \;=\;  G_f  \;/\;  7758 \; A \; h \; ( 1 - S_{wi} ) \; E_{gi} \) \( S_{wi} \;=\;  1 -  ( G_f  \;/\;  7758 \; A \; h \; n \; E_{gi} ) \) \( E_{gi} \;=\;  G_f  \;/\;  7758 \; A \; h \; n \; ( 1 - S_{wi} ) \)
Symbol	English	Metric
\( G_f \) = Free Gas in Place	\(ft^3\)	-
\( A \) = Drainage Area	\(ft^2\)	-
\( h \) = Thickness	\(ft\)
\( n \) = Porosity	\(dimensionless\)	-
\( S_{wi} \) = Initial Water Saturation	\(dimensionless\)	-
\( E_{gi} \) = initial gas Expansion Factor	\(ft^3 \;/\; bbl\)	-

Free gas in place, abbreviated as \(G_f\), is the total volume of natural gas that is present in a reservoir and is not dissolved in oil or water but exists in a free state.  This term is used in reservoir engineering and the oil and gas industry, as it represents a measure for evaluating the potential productivity of a gas reservoir.

Key Points about Free Gas in Place

Reservoir Rock  -  The porous rock in which the gas is stored.
Porosity  -  The measure of the void spaces in the rock, which can hold the gas.
Gas Saturation  -  The fraction of the pore space that is filled with free gas.
Reservoir Volume  -  The total volume of the rock containing the gas.