DT
Schlumbergerµs/ftSonic (Delta-T)
Compressional-wave slowness, or interval transit time — how long sound takes to cross a foot of formation. It yields sonic porosity, ties logs to seismic through acoustic impedance, and underpins geomechanics and pore-pressure work.
- Property
- Compressional Slowness
- Acoustic Slowness
- Quantity
- time per length
- µs/ft · ms/ft · ms/cm · ns/m · ns/ft · ms/m · 0.001 h/ft · min/m · min/ft · h/km · µs/in · s/m · s/cm · ms/in · µs/m · s/in · s/ft
- Typical range
- ~52.6–135.2 usec/ft
- µs/ft, from tight matrix (~40–55) to high-porosity or shale (>100)
Logging tool
No logging tool is associated with this curve.
Service company
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How it's measured
A transmitter fires an acoustic pulse; receivers time the first compressional arrival, giving slowness in µs/ft. Borehole-compensated arrays cancel tool tilt and hole-size effects.
How it's used
Sonic porosity (Wyllie or Raymer-Hunt-Gardner), synthetic seismograms and seismic ties via acoustic impedance, and inputs to mechanical properties and pore-pressure prediction.
Common gotchas
Cycle-skipping and noise spikes appear in rough hole or with weak signal; unconsolidated sands need a compaction correction; shale and gas complicate the porosity transform. Prefer corrected (DTC-type) curves when available.
In LAS files
Recorded as DT (or DTC, AC, SLOW) in µs/ft. Shear slowness (DTS) may accompany it in dipole-sonic runs.
Also seen with DT in real logs
Curves that appear alongside DT in the same wells across the public corpus.