Skin Factor from Pressure Transient Semilog Analysis Calculator
Enter the required inputs, confirm the units, and run the calculator to solve s. Review the formula source and assumptions before using the result in engineering work.
Calculation context and source notes
Skin Factor from Pressure Transient Semilog Analysis calculates skin factor for pressure transient analysis workflows in reservoir engineering. The page keeps the declared variables, units, source relationship, and output definition visible for technical review.
Use this formula when the listed inputs (Delta_p_1hr, m, k, phi, mu, c_t, r_w) are known and the assumptions behind the cited pressure transient analysis relationship match the engineering case being checked.
Solves for
s (dimensionless)
Best next page
Formula, variables, and sourceFormula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns s = 1.356994 dimensionless. Defaults demonstrate the implementation; they are not recommended field values.
500
80
50
0.2
2
0.00001
0.25
Input definitions
Delta_p_1hr
psiPressure Change in the First Hour of the Test
m
psi/cycleSemilog Straight-Line Slope
k
mDEffective Permeability
phi
fractionPorosity
mu
cPFluid Viscosity
c_t
1/psiTotal Compressibility
r_w
ftWellbore Radius
Output definitions
s
Skin Factor
Delta_p_1hr
Pressure Change in the First Hour of the Test
m
Semilog Straight-Line Slope
k
Effective Permeability
Engineering use, assumptions, and limits
Use this formula when the listed inputs (Delta_p_1hr, m, k, phi, mu, c_t, 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.
Frequently asked questions
What inputs does the Skin Factor from Pressure Transient Semilog Analysis calculator need?
The calculation uses Pressure Change in the First Hour of the Test (Delta_p_1hr), Semilog Straight-Line Slope (m), Effective Permeability (k), Porosity (phi), Fluid Viscosity (mu), Total Compressibility (c_t), Wellbore Radius (r_w). Enter values on the units shown beside each field.
What result does this calculator return?
The primary result is skin factor in dimensionless. The formula section shows the declared relationship, variables, and a reproducible default calculation.
What should I check before using the result?
Confirm the unit basis, source applicability, and input quality. The calculation does not replace a full engineering model or operating procedure. Mixing unit systems without converting the inputs.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
AAPG Wiki, Pressure transient testing, oil-well skin-factor equation after W. John Lee.
Open source reference