SFL
SchlumbergerΩ·cmSpherically Focused Log
A shallow-to-medium focused-current resistivity that reads the invaded zone. Run with deep induction (ILD) to profile invasion and refine the true-resistivity estimate.
- Property
- Spherically Focused Resistivity
- Shallow Resistivity
- Quantity
- electrical resistivity
- Ω·cm · kΩ·m · Ω·m²/m · nΩ·mm²/m · Ω·m · nΩ·mil²/ft
- Typical range
- ~1.6–144.7 ohm·m
- ohm·m, invaded-zone resistivity
Logging tool
No logging tool is associated with this curve.
Service company
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How it's measured
Spherical focusing shapes the survey current into a compact volume near the borehole, giving a shallow-reading resistivity relatively free of borehole and bed-thickness distortion.
How it's used
The shallow member of the induction triad (with ILM and ILD) for invasion analysis and Rxo estimation, and for bed-boundary definition thanks to its sharper vertical response.
Common gotchas
It reads the invaded zone, not Rt — separation from ILD indicates invasion, not necessarily hydrocarbons. It has largely been superseded by array-induction shallow curves in modern tools.
In LAS files
Recorded as SFL (or RSFL, RXO). Expect it alongside ILD and ILM in older induction logs.
Also seen with SFL in real logs
Curves that appear alongside SFL in the same wells across the public corpus.