Production EngineeringWell Performance
Single-Phase Gas Flow Subsonic Formula
Single-Phase Gas Flow Subsonic calculates standard gas flow rate for well performance workflows in production engineering.
How engineers use this formula
Use this formula when the listed inputs (P_d, P_u, k, A_choke, gamma_g, T_u, C_d) are known and the assumptions behind the cited well performance 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, q_sc equals 4,754.62753 Mscf/day.
P_dpsi
700
P_upsi
1000
kdimensionless
1.27
A_chokein^2
0.2
gamma_gair=1
0.65
T_udegR
600
C_ddimensionless
0.85
Inputs
P_d
psiDownstream Pressure
P_u
psiUpstream Pressure at Choke
k
dimensionlessSpecific Heat Ratio
A_choke
in^2Choke Cross-Sectional Area
gamma_g
air=1Gas Specific Gravity
T_u
degRUpstream Temperature
C_d
dimensionlessChoke Discharge Coefficient
Outputs
q_sc
Mscf/day
Standard Gas Flow Rate
Source and review
reviewedGuo, B., Lyons, W.C., and Ghalambor, A. Petroleum Production Engineering: A Computer-Assisted Approach, Page 5/61.
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