Rock Typing and Permeability · Module K6
Classes and their transforms
With a discriminator chosen, the plugs are split into classes and each class gets its own permeability transform. This module explains the one-dimensional clustering in log space, the four-plug minimum per class, what the silhouette score measures and why it cannot answer one, and how to read the rock types table. It compares a free power law with a constant FZI transform and shows how a narrow porosity window produces a runaway exponent.
- Level
- Advanced
- Position
- Module 6 of 8
- Video
- About 18 minutes, narrated
- Format
- Narrated video lesson with captions and slide reading view; with the certified option, a quiz whose pass unlocks the next module.
What the module covers
- Clustering a discriminator in log space
- Plug counts and the four-plug minimum
- What the silhouette score measures
- The rock types table, column by column
- Free power law or constant FZI
- How many rock types the plugs support
Learning outcomes
After the module you should be able to:
- Build a number of rock types you can explain from the rock, each with its own transform and fitted porosity range.
- Defend a rock type count from the rock and the plug counts, not the score alone
- Keep a class transform inside its fitted porosity range, or say why not
A short preview
A silhouette score rates how cleanly the plugs split into a chosen number of classes, from two to six. It never scores a single class. Run it on a well whose core came from one porosity to permeability relation and it still suggests two rock types, at 0.68, only a little below the 0.73 it gives the four real units of the course well. A good score cannot be the reason for a rock type. That reason has to come from the rock, from per-class lines that sit further apart than their own scatter, and from logs able to separate the classes.
Who it is for
Petrophysicists, reservoir engineers and geoscientists who build permeability curves from core and logs, define rock types, and carry permeability into net pay, k·h and saturation-height models.
Prerequisites: The Intermediate track, or working experience with shale volume, porosity and water saturation; Advanced modules A2 and A4 help but are not required. The hands-on steps use the Rock Typing, Permeability estimate, NMR and Neural network permeability workspaces in Formation Evaluation, all available from the Starter plan.
Take the module in the Learning Hub
Rock Typing and Permeability: Specialty course, sold separately: eight modules that turn core plugs and logs into a permeability curve you can defend, from plugs on a stated basis through transforms, NMR and rock types to net pay, k·h and the saturation-height hand-off. The lesson opens in the Learning Hub once the track is purchased; graded quizzes and the certificate come with the certified option.