Reservoir EngineeringPressure Transient Analysis
Radius of Investigation from Flow Time Formula
Radius of Investigation from Flow Time calculates radius of investigation 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) 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, r_i equals 765.525354 ft.
kmD
50
th
24
phifraction
0.18
mucP
1.2
c_t1/psi
0.00001
Inputs
k
mDPermeability
t
hFlow Time
phi
fractionPorosity
mu
cPOil Viscosity
c_t
1/psiTotal Compressibility
Outputs
r_i
ft
Radius of Investigation
k
mD
Permeability
t
h
Flow Time
phi
fraction
Porosity
mu
cP
Oil Viscosity
c_t
1/psi
Total Compressibility
Source and review
reviewedMatthews, C. S. and Russell, D. G. Pressure Buildup and Flow Tests in Wells, Page 116.
Source