Geophysical Mapping: Method Details
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Method Name: Borehole imaging, Structure logging
Method Type:   Borehole Methods
Assigned Problems:
+ Building stability Buildings and Structures
+ Cavity detection Civil Engineering
+ Depth of Overburden-bedrock interface Civil Engineering
+ Fractures Groundwater
+ Ice thickness Natural Hazards
+ Permafrost and ice detection Natural Hazards
+ Quality / Thickness of concrete Buildings and Structures
+ Quality and thickness (Natural resources) Natural Resources
+ Soil / rock quality Civil Engineering
0 Characteristics of hazardous waste Hazardous Waste
0 Contaminant plumes Hazardous Waste
0 Earthquakes / paleoseismology Natural Hazards
0 Foundations of ancient structures Buildings and Structures
0 Groundwater table Groundwater
0 Heat mining Natural Resources
0 Host sediments, hydogeological settings Hazardous Waste
0 Landslides Natural Hazards
0 Porosity / Permeability Groundwater
0 Quality / Thickness of aquifer/aquitard Groundwater
   '+' = Technique applicable; '0' = Application possible/limited use
Principle:   Imaging the borehole wall with television logs (colour optical image), acoustic borehole televiewer (BHTV: acoustic televiewer) (colored image of the reflected amplitudes) or electrical imaging (colored image of resistivity).
Keywords:   Seisviewer; circumferential borehole imaging (CBIL); borehole televiewer (BHTV); formation microImager; Formation MicroScanner (FMS)
  • Fluid filled borehole (exception: borehole television / optical scanner)
  • Television log: optic transparent borehole fluid
  • Smooth borehole wall is favourable
  • Excentric or oval boreholes should be avoided
  • Suspended particles in the fluid may scatter seismic waves and degrade the acoustic imaging
  • Acoustic televiewer: maximum borehole diameter is about 20 cm
  • Seismic velocity in the borehole fluid should be lower than in the surrounding rock
  • Instrument dependent (logging speed)
  • Acoustic televiewer: about 2 cm or smaller
  • The depth of investigation is limited to the borehole-wall surface
Expected Results:  
  • Measured parameter: optical or coloured images of the borehole wall (real-time)
  • Data analysis: colors represent the amplitude values
  • Interpretation: Identification of fractures; fracture width and orientation; direction of tectonical stress
Combination with other Methods:  
  • Required additional information other loggings; cores
  • Related add-on information: combination of borehole imaging techniques (e.g. resistivity imager and acoustic televiewer); caliper log
  • Independent additional information: other logs; cores
Operating Expense:  
  • Crew size:2 persons
  • Acquisition speed: logging speed 1.2 - 2.5 m / min
  • Processing: expensive
  • Equipment rental costs: high
Parameters to specify:  
  • Instrument type
  • Sampling rate (digital device)
  • Logging speed (1.2 - 2.5 m / min)
  • Properties of borehole filling fluids
QC Documents:  
  • Calibration data: last laboratory-calibration and on-site calibration
  • Around 20 m of repeated measurements
  • Borehole information (i.e., casing type, length, diameter, deviation, fluid properties)
  • Complete headers
  • Field notes (e.g., all activities, effective time schedule, present personnel)
  • Pictures of the borehole wall
  • Statistical presentation (3-D or planar view) or the structural data
  • Results of acoustic borehole televiewer
  • Results of electromagnetic imaging
  • Field logs (displayed using specified scales)
  • Interpretation
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