Joshi Horizontal Well Productivity Index Calculator
Enter horizontal and vertical permeability, net thickness, horizontal well length, drainage radius, wellbore radius, oil viscosity, formation volume factor, and skin. The calculator evaluates the Joshi flow-resistance denominator and returns productivity index in STB/day/psi.
Calculation context and source notes
The Joshi horizontal well productivity index estimates steady-state oil deliverability for a centered horizontal well by combining horizontal and vertical flow resistance, drainage geometry, anisotropy, well length, fluid properties, and skin.
Use this relationship for early horizontal-well screening when the reservoir and fluid can reasonably be represented by the steady-state single-phase assumptions behind the Joshi model. Compare the result with a vertical-well case or a calibrated reservoir model before making a development decision.
Solves for
J_h (STB/day/psi)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns J_h = 7.506234 STB/day/psi. Defaults demonstrate the implementation; they are not recommended field values.
100
10
50
1000
40
0.328
2
1.2
0
Input definitions
k_h
mDHorizontal Permeability
k_v
mDVertical Permeability
h
ftNet Pay Thickness
L
ftHorizontal Well Length
A_ac
acresDrainage Area
r_w
ftWellbore Radius
mu_o
cPOil Viscosity
B_o
bbl/STBOil Formation Volume Factor
s
dimensionlessSkin Factor
Output definitions
J_h
Horizontal Well Productivity Index
A_ft2
Drainage Area
r_eh
Horizontal Drainage Radius
beta
Permeability Anisotropy Coefficient
a_joshi
Semi-Major Axis of Elliptical Drainage Area
R_h
Joshi Horizontal Drainage Ratio
D_joshi
Joshi Productivity Denominator
Engineering use, assumptions, and limits
Use this relationship for early horizontal-well screening when the reservoir and fluid can reasonably be represented by the steady-state single-phase assumptions behind the Joshi model. Compare the result with a vertical-well case or a calibrated reservoir model before making a development decision.
Assumptions
- The horizontal well is represented by the Joshi steady-state inflow geometry and is centered vertically unless the selected inputs explicitly account for another case.
- Single-phase oil properties and permeability are representative over the drainage volume.
- Horizontal and vertical permeability capture the reservoir anisotropy used by the model.
Limitations
- Does not model transient startup, multiphase relative permeability, pressure-dependent PVT, fractures, or wellbore pressure loss along the lateral.
- Drainage dimensions and skin can dominate the result and should not be inferred from the calculator defaults.
Common mistakes
- Using total well length where the equation requires completed horizontal length.
- Assuming vertical permeability equals horizontal permeability without evidence.
- Comparing the calculated index with a field rate without using the same pressure drawdown and fluid basis.
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.
Joshi, S.D. 1988. Augmentation of Well Productivity With Slant and Horizontal Wells; Petroleum Office horizontal well productivity documentation.
Open source reference