Reservoir EngineeringPressure Transient Analysis
Radius of Investigation from Shut-In Time Formula
Radius of Investigation from Shut-In 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, Delta_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
Delta_th
24
phifraction
0.18
mucP
1.2
c_t1/psi
0.00001
Inputs
k
mDPermeability
Delta_t
hShut-In Time
phi
fractionPorosity
mu
cPOil Viscosity
c_t
1/psiTotal Compressibility
Outputs
r_i
ft
Radius of Investigation
k
mD
Permeability
Delta_t
h
Shut-In 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 117.
Source