Gas Material Balance Equation Formula
Gas Material Balance Equation calculates current pressure to compressibility factor ratio for material balance workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (P_i_z_i, P_sc, T, T_sc, V, G_p) 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, P_z equals 3,983.038462 psi.
4000
14.7
600
520
1000000000
1000000000
Inputs
P_i_z_i
psiInitial Pressure to Compressibility Factor Ratio
P_sc
psiaStandard Pressure
T
°RReservoir Temperature
T_sc
°RStandard Temperature
V
ft³Original Gas Volume
G_p
SCFCumulative Gas Production
Outputs
P_z
Current Pressure to Compressibility Factor Ratio
P_i_z_i
Initial Pressure to Compressibility Factor Ratio
P_sc
Standard Pressure
T
Reservoir Temperature
T_sc
Standard Temperature
V
Original Gas Volume
G_p
Cumulative Gas Production
Source and review
reviewedAhmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 203.
Source