NMR Interpretation Module
Purpose
The NMR interpretation module allows users to calculate porosity, bound and free fluids from the measure T1 and T2 distributions from NMR tools.
Primary Outputs
| Curve Name | Description |
|---|---|
| PHIT_NMR | Total porosity from NMR |
| TOTAL_BOUND_FLUID_VOLUME | Total bound fluid volume |
| CLAY_BOUND_WATER_VOLUME | Clay bound water volume |
| SWIRR_NMR | Irredducible Sw from NMR |
| PERM_COATES_NMR | Permeability from NMR using Coates method |
Discussion
In oil and gas well logging, the $T_2$ distribution is used as a high-resolution "map" of the formation's pore system. While a standard porosity tool tells you how much fluid is there, NMR tells you where that fluid is trapped and whether it will flow.
The raw data is converted into a T2 distribution (a plot of amplitude vs. relaxation time).
- Small pores (high surface-to-volume ratio) cause fast relaxation.
- Large pores (low surface-to-volume ratio) cause slow relaxation.
Petrophysicists use "cutoffs" to divide the total porosity into functional components. These values vary by lithology:
| Component | Clastics | Carbonates | Interpretation |
|---|---|---|---|
| Clay Bound Water | < 3ms | Variable | Water chemically bound to clays; non-producible. |
| Bulk Volume Irreducible | 3-33ms | 3-90ms | Capillary-bound water; held by surface tension; non-producible. |
| Free Fluid | > 33ms | > 90ms | "Free Fluid Index"; the oil, gas, or water that can actually flow. |
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Sample data to get started
Need some sample data to get started? The files below are from data made public by the Wyoming Oil and Gas Commission. These will allow you to get started with petrophysics, mapping, and decline curve analysis. Well header data Formation tops data Deviation survey data Well log data (las files) Production data (csv) or (excel) Wyoming counties shapefile and projection Wyoming townships shapefile and projection Haven’t found the help guide that you are looking for?
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