Reservoir EngineeringPressure Transient Analysis
Dimensionless Radius of Radial Flow – Constant-Rate Production Formula
Dimensionless Radius of Radial Flow – Constant-Rate Production calculates dimensionless radius for pressure transient analysis workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (r, r_w) 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_d equals 3,333.333333 dimensionless.
rft
1000
r_wft
0.3
Inputs
r
ftEffective Radius or Reservoir Radius
r_w
ftWellbore Radius
Outputs
r_d
dimensionless
Dimensionless Radius
r
ft
Effective Radius or Reservoir Radius (rearranged)
r_w
ft
Wellbore Radius (rearranged)
Source and review
reviewedLee, J., Rollins, J. B., & Spivey, J. P. (2003). Pressure Transient Testing (Vol. 9). Richardson, Texas: Society of Petroleum Engineers, Page: 8.
Source