Rock Typing and Permeability · Module K4
Permeability from NMR
NMR measures directly what the transforms can only estimate: the bound water volume and the pore size. This module covers the T2 array and its time axis, the partition into clay-bound, capillary-bound and free fluid, the sandstone and carbonate cut-offs, and the Coates and SDR permeability models. It scores both against core by rock type, shows what a wrong cut-off does, and calibrates the constants by hand.
- Level
- Advanced
- Position
- Module 4 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
- The T2 array, its time axis and amplitude units
- Clay-bound, capillary-bound and free fluid
- Sandstone and carbonate T2 cut-offs
- The Coates and SDR permeability models
- Scoring both against core by rock type
- Hydrocarbon effects on the T2 spectrum
Learning outcomes
After the module you should be able to:
- State an NMR permeability's cut-off and constant, and score it against core in sand and in carbonate.
- Set the T2 axis, cut-off and model constant for the rock, and state them
- Calibrate an NMR permeability to core without hiding its spread by rock type
A short preview
Two NMR models turn a T2 distribution into permeability. Coates uses the ratio of free to bound fluid: at 20 porosity units, a ratio of 4 and the default constant of 10, it gives 256 millidarcies. SDR uses the logarithmic mean T2 instead: at a porosity of 0.20 and a mean of 100 ms, the sandstone coefficient of 4 gives 64 millidarcies. Choose the carbonate preset and that coefficient falls to 0.1, forty times lower, while the cut-off between bound and free fluid moves from 33 to 92 ms. Those two settings can change the answer more than the log does.
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.