Geophysical Mapping: Method Details
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Method Name: Acoustic logging
Method Type:   Borehole Methods
Assigned Problems:
+ Depth of Overburden-bedrock interface Civil Engineering
+ Fractures Groundwater
+ Gravel, clay, limestone, salt exploration Natural Resources
+ Porosity / Permeability Groundwater
+ Quality / Thickness of aquifer/aquitard Groundwater
+ Quality and thickness (Natural resources) Natural Resources
+ Soil / rock quality Civil Engineering
+ Young's / shear modulus, Poisson's ratio Civil Engineering
0 Building stability Buildings and Structures
0 Characteristics of hazardous waste Hazardous Waste
0 Groundwater table Groundwater
0 Heat mining Natural Resources
0 Host sediments, hydogeological settings Hazardous Waste
0 Ice thickness Natural Hazards
0 Landslides Natural Hazards
0 Permafrost and ice detection Natural Hazards
0 Quality / Thickness of concrete Buildings and Structures
   '+' = Technique applicable; '0' = Application possible/limited use
Principle:   Ultra-sonic waves are used to characterize the acoustic properties of the surrounding rock. Those are seismic velocities, attenuation of seismic amplitudes and reflection characteristics.
Keywords:   Sonic log; transit-time log; seismic velocities; attenuation of seismic amplitudes; reflection characteristics
Prerequisites:  
  • Layers must have sufficient velocity contrast and thickness
  • Uncased or bonded cased boreholes
  • Fluid filled borehole
  • Seismic velocity in the borehole fluid should be lower than in the surrounding rock
Resolution:   Typically resolution is 30 cm (1 ft) or 60 cm (2 ft)

Depth of investigation is 10 - 20 cm
Expected Results:  
  • Measured parameter: slowness in s / m
  • Data analysis: log of the seismic velocity in m / s or full waveform (acoustic log/sonic log; full-waveform sonic log)
  • Interpretation: porosity, elastic parameters
Combination with other Methods:  
  • Required additional information: density log for calculation of elastic parameters necessary
  • Related add-on information: caliper log
  • Independent additional information: other logs; laboratory analyses
Operating Expense:  
  • Crew size: 2 persons
  • Acquisition speed: logging speed 2 - 4 m / min
  • Processing: intermediate
  • Equipment rental costs: high
Parameters to specify:  
  • Instrument type
  • Sampling rate (digital devices)
  • Logging speed (2 - 4 m / min)
  • Properties of borehole filling fluids
QC Documents:  
  • Calibration data: last laboratory-calibration
  • Around 20 m of repeated measurements
  • Borehole information (i.e., casing (type and length), diameter, deviation, fluid properties)
  • Complete headers
  • Field notes (e.g., all activities, effective time schedule, present personnel)
Products:  
  • Field logs (displayed using specified scales)
  • Composite logs
  • Crossplots
  • Listings; histograms
  • Interpretation
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