Time to Semi-Steady State for Gas Well Drainage Area Formula
Time to Semi-Steady State for Gas Well Drainage Area calculates time to semi-steady state for pressure transient analysis workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (phi, mu_gi, c_ti, A, k) are known and the assumptions behind the cited pressure transient analysis 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, t_pss equals 0.7584 h.
0.12
0.02
0.00001
1000000
0.5
Inputs
phi
fractionPorosity
mu_gi
cPInitial Gas Viscosity
c_ti
1/psiInitial Total Compressibility
A
ft^2Drainage Area
k
mDEffective Gas Permeability
Outputs
t_pss
Time to Semi-Steady State
phi
Porosity
mu_gi
Initial Gas Viscosity
c_ti
Initial Total Compressibility
A
Drainage Area
k
Effective Gas Permeability
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 194.
Source