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Optical Imager Tool
A precision-machined prism and CCD camera assembly permits a high definition optical image of the borehole wall to be captured in a variety of horizontal and vertical resolutions.
The resulting image is digitised in the tool for transmission to the surface acquisition system. The image is then orientated to North and displayed as an unwrapped image log. This enables a detailed structural interpretation to be made if required.
For the best results the optical imager should be run above the water level or in clean, clear fluid.
Features and benefits
- Tool centralised during data acquisition by two sets of bowsprings
- Image viewed and recorded on way down borehole to limit disturbance to the clarity of any water present
- Orientation system employs a flux gate magnetometer and therefore data within approximately one metre of steel casing is un-orientated
- Structural features and discontinuities are hand picked from the images in form of colour coded sinusoidal projections
Specifications
Logging Conditions
- 0.5−6m/min
- Centralised
Borehole Conditions
- Minimum diameter 75mm
- Maximum diameter 500mm
- Dry or clear water filled unlined
Presentation of results
- Detailed logs of imager data can be produced at any vertical scale, though 1:20 is commonly used
- Using the borehole diameter, tilt and azimuth, along with the geometric parameters of the sinusoids, the true azimuth and dip of the discontinuities are calculated and presented as a “tadpole” plot (True Dip ˚). The horizontal position of the tadpoles head gives the defects‘ true dip angle and its tail points in the direction of the defects azimuth
- Discontinuities pick form the Imager log can be presented as Rose Diagrams, Stereonets, Frequency Histograms or Contour plots
Optical image examples