BS
Schlumbergeryd[US]Bit Size
The drill-bit diameter for the logged interval — the reference gauge hole size the caliper is compared against to find washouts and mudcake. Not a measurement but a recorded drilling parameter.
- Property
- Nom Borehole Diameter
- Borehole Diameter
- Quantity
- length
- yd[US] · link[Cla] · µm · m[Ger] · nm · Mm · yd[Ind37] · link[BnB] · ft[BnB] · 100 ft · yd[Cla] · yd[SeT] · 0.1 ft · ft · link[BnA] · ft[BnA] · ft[GC] · 0.1 ft[US] · 1/64 in · ft[Ind62] · km · 100 km · yd[Ind] · fur[US] · 0.1 yd · chain[SeT] · in · mil · chain[BnB] · mm · yd[Se] · mi · mi[naut] · 1/² ft · ft[Br65] · Gm · Em · rod[US] · fathom · ångström · ft[Cla] · dm · ft[Ind37] · chain · chain[Cla] · link[SeT] · link[US] · ft[US] · chain[Ind37] · link[Se] · yd[Ind75] · hm · m · ft[Ind75] · in[US] · chain[Se] · dam · 1/32 in · ft[Se] · 30 ft · yd[BnA] · fm · chain[BnA] · mi[US] · Tm · link · 10 km · ft[Ind] · ft[SeT] · 10 ft · 0.1 in · yd · 1000 ft · 10 in · pm · chain[US] · cm · 30 m · 1/16 in · yd[BnB] · ft[Br36] · mi[nautUK] · yd[Ind62]
- Typical range
- ~7.9–7.9 in
- inches, nominal hole size
Logging tool
No logging tool is associated with this curve.
Service company
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How it's measured
Entered from the bit record rather than measured downhole: the nominal diameter of the bit used to drill the interval, held constant (or stepped) over each hole section.
How it's used
The baseline for hole-condition analysis — caliper greater than bit size marks washouts and breakouts, caliper less than bit size marks mudcake on permeable beds. Also an input to borehole environmental corrections.
Common gotchas
It is a constant reference, not a log — a flat trace is expected and correct. It reflects the bit, not the actual hole, so it only carries meaning next to the caliper.
In LAS files
Recorded as BS (or BITSIZE) in inches, usually a constant per interval. Always interpreted together with CALI.
Also seen with BS in real logs
Curves that appear alongside BS in the same wells across the public corpus.