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Method Name: |
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Borehole imaging, Structure logging |
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Method Type: |
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Borehole Methods
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Assigned Problems: |
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Principle: |
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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). |
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Keywords: |
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Seisviewer; circumferential borehole imaging (CBIL); borehole televiewer (BHTV); formation microImager; Formation MicroScanner (FMS) |
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Prerequisites: |
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- 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
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Resolution: |
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- Instrument dependent (logging speed)
- Acoustic televiewer: about 2 cm or smaller
- The depth of investigation is limited to the borehole-wall surface
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Expected Results: |
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- 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
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Combination with other Methods: |
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- 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
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Operating Expense: |
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- Crew size:2 persons
- Acquisition speed: logging speed 1.2 - 2.5 m / min
- Processing: expensive
- Equipment rental costs: high
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Parameters to specify: |
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- Instrument type
- Sampling rate (digital device)
- Logging speed (1.2 - 2.5 m / min)
- Properties of borehole filling fluids
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QC Documents: |
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- 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)
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Products: |
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- 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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