The Borehole Televiewer (BHTV) provides and acoustic"image" of the borehole wall by scanning it with narrow pulsed acoustic beam from rotating transducer while the tool is pulled up the hole. The amplitude and travel time of acoustic signals reflected from the wall are measured with the same transducer that generates the acoustic beam. A magnetic sensor is used to orientate the images which are continuously displayed on screen and stored on digital tape. A hard-copy log may be printed.

BRG maintains a slim hole BHTV for land based logging projects.

The main advantages of the BHTV - high resolution and full 360 degree coverage of the hole circumference. The tool provides detailed information for:

1. Investigation of fractures. Location, size, and orientation of fractures intersecting the wellbore can be determined.
   
   
2. Stress analysis. Characterize borehole breakouts of directional measurements of in-situ stress field.
   
   
3. Thin bed evolution. Structural features such as bedding in sediments, and the character and distribution of pillow basalts in the ocean crust. Bedding planes and core orientation (dipmeter).
   
   
4. Rock texture
   
   
5. Physical properties (acoustic impedance)
   
   
6. Study of borehole form and stability
   
   

1. Environmental effects: Common problem limiting BHTV applications - heavy mud (over 1.3 g/cm³), or mud containing sound attenuating ingredients (barite). Excessive hole diameter and/or cavities over 14 in. also impair results. Centralizing of the tool is a must.
   
   
2. Vertical resolution: Depends on logging speed and changes from 0.5 in. to 3 in. with respective logging speeds of 450 to 2600 ft/hr.
   
   
3. Horizontal resolution: Depends on signal frequency, sampling rate, and hole diameter but in most cases remains in the 0.15 in. - 0.3 in. range.
   
   
4. Note: due to reflections overlapping and high sensitivity of the tool to acoustic impedance changes, structural objects (fractures, etc.) with sizes much less then horizontal resolution could be detected.
   
   

The BHTV travel time and signal amplitude data usually are displayed as color coded maps with depth and orientation information. Vertical fractures appear as straight lines, while fractures dipping between vertical and horizontal appear as sinusoidal traces.

In addition, the caliper information can be shown for specified depths as a hole cross section.