Indonesian Shaly Sand Water Saturation Calculator
Enter true formation resistivity, shale resistivity, formation-water resistivity, effective porosity, shale volume, and the lithology and saturation exponents. The result is fractional water saturation; review any value outside zero to one before use.
Calculation context and source notes
The Poupon-Leveaux Indonesian equation estimates water saturation in shaly formations by combining formation-water and shale conductivity terms with effective porosity, shale volume, true resistivity, and saturation exponents.
Use the Indonesian model when clean-sand Archie assumptions are inadequate because conductive shale contributes materially to the measured formation response. Validate shale volume, shale resistivity, water resistivity, and saturation parameters against local core and log interpretation practice.
Solves for
S_w (fraction)
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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 S_w = 0.214387 fraction. Defaults demonstrate the implementation; they are not recommended field values.
20
0.2
2.5
0.2
2
1
0.05
2
Input definitions
R_t
ohm mTrue Formation Resistivity
V_sh
fractionVolume of Shale
R_sh
ohm mWet Shale Resistivity
phi_e
fractionEffective Porosity
m
dimensionlessCementation Exponent
a
dimensionlessTortuosity Factor
R_w
ohm mFormation Water Resistivity
n
dimensionlessSaturation Exponent
Output definitions
S_w
Water Saturation
Engineering use, assumptions, and limits
Use the Indonesian model when clean-sand Archie assumptions are inadequate because conductive shale contributes materially to the measured formation response. Validate shale volume, shale resistivity, water resistivity, and saturation parameters against local core and log interpretation practice.
Assumptions
- Effective porosity and shale volume are on a consistent fractional basis.
- The selected shale resistivity represents the conductive shale component in the logged interval.
- Water resistivity and formation resistivity are corrected to compatible conditions.
Limitations
- The empirical shale-conductivity treatment may not represent every clay type, laminated geometry, salinity regime, or low-resistivity pay mechanism.
- Saturation parameters should be calibrated where core or capillary-pressure data are available.
Common mistakes
- Entering porosity or shale volume as percentages instead of fractions.
- Mixing resistivities corrected to different temperatures.
- Using a generic shale resistivity from another interval without checking log character and mineralogy.
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.
Evaluation of Water Saturation in Shaly Formations, Poupon, A., Leveaux, J. (1971)
Poupon, A. and Leveaux, J. 1971. Evaluation of Water Saturation in Shaly Formations. SPWLA 12th Annual Logging Symposium; Nafta Wiki formula entry for Indonesia Model.
Open source reference