Rock Typing and Permeability · Module K7
Rock type down the well
Core covers a fraction of the well, so rock types have to be predicted from logs before a permeability curve can be written. The module explains the naive Bayes classifier, the choice of up to three log curves, leave-one-out accuracy against a plain guess, and the confusion matrix. It then covers the shale gate, the confidence floor and samples outside each type's cored porosity, and scores the prediction against truth in the uncored section.
- Level
- Advanced
- Position
- Module 7 of 8
- Video
- About 16 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
- A classifier you can audit
- Choosing log curves that see the rock
- Leave-one-out accuracy against a baseline
- Reading the confusion matrix
- The shale gate and the confidence floor
- Porosity outside the cored range
Learning outcomes
After the module you should be able to:
- Save a rock type and permeability curve with the classifier's skill, the gated count and the out-of-range count stated.
- Show that the chosen logs separate the rock types before a prediction is saved
- Report the gated, blanked and out-of-range counts with the saved curves
A short preview
Before a classifier carries rock types away from the core, test it. Leave each plug out in turn, predict its type from the logs, and count the hits. On the course well, gamma ray, neutron and resistivity get 95 percent right, against 32 percent for always guessing the most common type. Caliper and density correction manage 29 percent, worse than the guess. Passing is not the end of it: the classifier always answers with one of its trained types, so with the reservoir gate switched off a shale still receives a rock type, at full confidence.
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.