Acoustic Televiewer

Parameters Logged:

Acoustic Amplitude / Acoustic Travel Time

Ultrasonic transducer

50mm to 500mm hole size applications

Borehole Azimuth and Dip

Tri axial Magnetometers and Accelerometers

+/- 1.00 Az, +/-0.20 Dip

Natural Gamma

Scintillation Crystal 25.4mm x 101.6mm

0-10,000 API units

Primarily used for geotechnical observations the televiewer takes an oriented acoustic image of the borehole wall by transmitting ultrasound pulses from a rotating sensor. It records the amplitude and travel time of the signals reflected at the interface between bore hole fluid and formation (borehole wall).

Televiewers (both Optical and Acoustic) can reduce the reliance on coring for geotechnical observation by obtaining structural information from less expensive percussion holes. They can also give more detailed structural information than traditional orientated core and can provide orientation data in vertical holes.

Applications:

The travel time is used to determine exceptionally accurate borehole diameter data (>0.1mm), which makes the tool ideal for borehole deformation description (stress field analysis) and casing inspection.

The amplitude of the reflection from the borehole wall is representative of the acoustic (elastic) properties of the surrounding rock. Therefore, the tool is ideal for fracture detection and geotechnical rock classification. Cement bond quality can be checked if the reflection signal from behind casing is analysed. The tool must be run centralised (or in centralised PVC) in open, fluid filled holes.

The most common applications are:

• fracture detection and evaluation
• detection of thin beds
• determination of bedding dip and orientation
• lithological characterisation
• breakout analysis
• monitoring of earth stress field
• casing inspection
• high resolution calliper measurements