Gas Saturation in Water-Drive Gas Reservoirs Formula
Gas Saturation in Water-Drive Gas Reservoirs calculates gas saturation for material balance workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (G, G_p, B_g, B_gi, W_e, W_p, B_w, S_wi, S_grw) are known and the assumptions behind the cited material balance relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, S_g equals 0.779302 fraction.
1000000000
200000000
0.005
0.004
200000
50000
1.02
0.25
0.15
Inputs
G
SCFGas Initially in Place
G_p
SCFCumulative Gas Production
B_g
bbl/SCFCurrent Gas Formation Volume Factor
B_gi
bbl/SCFInitial Gas Formation Volume Factor
W_e
bblCumulative Water Influx
W_p
STBCumulative Water Production
B_w
rb/STBWater Formation Volume Factor
S_wi
fractionInitial Water Saturation
S_grw
fractionResidual Gas Saturation to Water Displacement
Outputs
S_g
Gas Saturation
Source and review
reviewedAdvanced Reservoir Engineering, Ahmed, T., McKinney, P. D. (2005)
Ahmed, T. and McKinney, P. D. 2005. Advanced Reservoir Engineering. Gulf Publishing of Elsevier, Chapter 3, Page 208.
Source