The Optical Imager contains a precision machined prism and high definition digital camera assembly which permits high quality images of the borehole wall to be recorded at 0.5mm intervals vertically and 720 pixels per
360° horizontally.
The Acoustic Imager produces an image of the borehole wall using the travel time and amplitude of an acoustic signal transmitted and received by the tool. The variance of the acoustic properties of the formation and associated features enable the nature of fractures, fissures, veins, bedding planes and lithological changes to be determined. The acoustic image below shows both fractures and steeply dipping bedding.
Additionally, rose diagrams and stereo-nets of the discontinuities can be produced.The plots can then be transferred into various electronic formats.
Detailed logs of the imager data can be produced at any vertical scale, though 1:20 is commonly used. All images are referenced to Magnetic North. The image of the borehole wall is presented in an unwrapped form with a horizontal scale marked 0°- North, through 90°- East, 180°- South, 270°-West, back to North.
Structural features and discontinuities are picked from the images in the form of colour coded sinusoidal projections blue - fractures, red -bedding/fabric features, green - veins. This structural log is presented as ‘Discontinuities’ witha horizontal scale marked 0°, North, through 90°,East, 180°, South, 270°, West, back to North.
Using the borehole diameter, dip and azimuth 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. These logs are presented with a horizontal scale in degrees. By convention the top of the page is North (Magnetic)and the right hand edge of the paper is East.