CALI
SchlumbergerinCaliper
Borehole diameter measured by mechanical arms. It reads near bit size in gauge hole, larger across washouts and breakouts, and smaller where mudcake builds on permeable beds — the primary hole-quality log and a correction input for every pad tool.
- Property
- Borehole Diameter
- Inside Diameter
- Quantity
- length
- Typical range
- ~4.1–11.4 in
- inches, relative to bit size
Logging tool
No logging tool is associated with this curve.
Service company
Browse the full Schlumberger mnemonic dictionary, including legacy and current tool families.
View Schlumberger mnemonics →What is the CALI curve?
How it's measured
One or more spring-loaded arms track the borehole wall; their extension is converted to a diameter. Multi-arm calipers also capture hole shape and ovality.
How it's used
Hole-quality QC and an essential correction input for density, neutron, and sonic logs, which lose pad contact in rugose hole. Where the caliper reads less than bit size, mudcake flags a permeable, porous zone.
Common gotchas
A hole much larger than bit size warns that pad-contact logs (RHOB, DRHO, PEF) may be unreliable there. Key-seating and breakouts make single-arm readings direction-dependent.
In LAS files
Recorded as CALI (sometimes CAL, CALX/CALY for multi-arm) in inches. Compare it against BS to spot washouts and mudcake.
Also known as
Variants of CALI seen in real LAS files — PetroCurve maps each of these on import.
Based on 6,700,555 samples in the public corpus.
Also seen with CALI in real logs
Curves that appear alongside CALI in the same wells across the public corpus.