Dimensionless Time for Interference Testing in Homogeneous Reservoirs – Earlougher Formula
Dimensionless Time for Interference Testing in Homogeneous Reservoirs – Earlougher calculates dimensionless time for pressure transient analysis workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (k, t, phi, mu, c_t, rw) 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_D equals 23,440,000 dimensionless.
100
24
0.2
0.25
6e-6
0.3
Inputs
k
mDPermeability
t
hrElapsed Time
phi
fractionPorosity
mu
cPViscosity
c_t
1/psiTotal Compressibility
rw
ftWellbore Radius
Outputs
t_D
Dimensionless Time
k
Permeability (rearranged)
t
Elapsed Time (rearranged)
phi
Porosity (rearranged)
mu
Viscosity (rearranged)
c_t
Total Compressibility (rearranged)
rw
Wellbore Radius (rearranged)
Source and review
reviewedEarlougher, R.C. (1977). Advances in Well Test Analysis. SPE Monograph Series, Vol. 5, Page: 8.
Source