Pore Pressure Gradient - Rehm and McClendon Calculator
Enter the required gradient and correction terms from the source equation. The calculator returns estimated pore pressure gradient.
Calculation context and source notes
The Rehm and McClendon pore pressure gradient relationship estimates formation pore-pressure gradient from drilling or formation-evaluation indicators used in well planning.
Use it for pore-pressure screening, mud-window review, and well-control margin awareness before detailed geomechanics calibration.
Solves for
g_p (psi/ft)
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Formula, variables, and sourceFormula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns g_p = 0.94124 psi/ft. Defaults demonstrate the implementation; they are not recommended field values.
2.8
1.2
Input definitions
d_cn
dimensionlessNormal Corrected d-Exponent
d_co
dimensionlessObserved Corrected d-Exponent
Output definitions
g_p
Pore Pressure Gradient
d_cn
Normal Corrected d-Exponent
d_co
Observed Corrected d-Exponent
Engineering use, assumptions, and limits
Use it for pore-pressure screening, mud-window review, and well-control margin awareness before detailed geomechanics calibration.
Assumptions
- The Rehm and McClendon relationship is appropriate for the local basin and data type.
- Input gradients and correction factors are calibrated to the interval being evaluated.
- The result is checked against independent pressure indicators where available.
Limitations
- Does not replace formation tests, calibrated seismic/geomechanical models, or pore-pressure specialist review.
- May be unreliable where compaction trends, lithology, or stress conditions differ from source assumptions.
Common mistakes
- Using a generic normal-compaction trend without local calibration.
- Confusing pressure gradient with total pressure.
- Using screening gradients directly as operational mud-weight limits.
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.
Advanced Well Control, Watson, D., Brittenham, T., Moore, P.L. (2003)
Watson, D., Brittenham, T. and Moore, P.L. 2003. Advanced Well Control, SPE Textbook Series Vol. 10, Page 52.
Open source reference