Intermediate Petrophysics · Module I2
Lithology and Shale Modeling
Shale volume and lithology are settled before porosity because every porosity and saturation model depends on them. The module covers the gamma-ray index and its non-linear transforms, SP and density–neutron estimates of Vsh, clastic and carbonate mineral responses, and an introduction to multi-mineral models, with the emphasis on documenting why a method was chosen.
- Level
- Intermediate
- Position
- Module 2 of 8
- Video
- About 18 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
- What Vsh measures and what it does not
- The gamma-ray index with linear and Larionov transforms
- SP and density–neutron shale indicators
- Clastic and carbonate mineral log responses
- An introduction to multi-mineral models
- Thin beds and the risk of over-correcting
Learning outcomes
After the module you should be able to:
- Build and justify lithology and Vsh assumptions.
- Compute Vsh by several methods and choose between them for a given rock
- Recognise the minerals that make the gamma ray misleading
- Document lithology choices with their uncertainty
A short preview
The gamma-ray index, IGR = (GR − GRclean) / (GRshale − GRclean), is a ratio, not a shale volume. Turning it into Vsh takes a transform, and the transforms disagree: at an index of 0.4 the linear relation gives 0.40, Larionov's equation for older rocks about 0.24, and his equation for Tertiary rocks about 0.15. Which one applies is a property of the rock, and it should be settled against core or a second indicator, not chosen because it gives the cleaner-looking answer.
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.