Intermediate Petrophysics · Module I4
Saturation Model Comparison
Archie's parameters and their ranges, Rw estimation, and why Archie fails in clay-rich rock, followed by the main shaly-sand models: Waxman–Smits, dual water and Indonesia. The module runs several models on the same data and treats the spread between them as model uncertainty to be carried forward.
- Level
- Intermediate
- Position
- Module 4 of 8
- Video
- About 20 minutes, narrated
- Format
- Narrated video lesson and slide reading view; with the certified option, a quiz whose pass unlocks the next module.
What the module covers
- Archie's a, m and n: meaning, ranges and defaults
- Estimating formation water resistivity
- Why clay conductivity breaks Archie
- Waxman–Smits and cation exchange capacity
- The dual water and Indonesia models
- Running several models on one dataset and reporting the spread
Learning outcomes
After the module you should be able to:
- Compare Sw models and document parameter/model risk.
- Choose and justify a saturation model for a shaly sand
- Quantify how much Sw changes between models and parameters
- Carry model uncertainty into the volumetric inputs
A short preview
Run Archie, Simandoux and Indonesia on the same sand, with effective porosity 0.20, Rt 10 ohm·m, Rw 0.05 ohm·m, 25 percent shale at 2 ohm·m and m = n = 2, and the water saturations come out at 0.35, 0.28 and 0.29. None of them is the true saturation. Each embodies a different assumption about how clay conducts, and the gap between them is part of the uncertainty of the interpretation. The module treats that gap as an input to be reported, not a choice to be hidden.
Who it is for
Petrophysicists and geoscientists with some interpretation experience, and engineers who review petrophysical inputs before they reach a volumetric or simulation model.
Prerequisites: The Basic Petrophysics track, or equivalent working experience.
Take the module in the Learning Hub
Intermediate Petrophysics: Eight applied modules with checkpoints; with the certified option, pass each quiz to unlock the next lesson. The lesson opens in the Learning Hub once the track is purchased; graded quizzes and the certificate come with the certified option.