Image Logs

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Exploration Technique: Image Logs

Exploration Technique Information
Exploration Group: Downhole Techniques
Exploration Sub Group: Well Log Techniques
Parent Exploration Technique: Well Log Techniques
Information Provided by Technique
Lithology: Identify different lithological layers, rock composition, grain size, mineral, and clay content
Stratigraphic/Structural: -Fault and fracture identification

-Rock texture, porosity, and stress analysis

-determine dip, thickness, and geometry of rock strata in vicinity of borehole

-Detection of permeable pathways, fracture zones, faults

Hydrological: Locate zones of aquifer inflow/outflow
Cost Information
Low-End Estimate (USD): 1.00100 centUSD
1.0e-3 kUSD
1.0e-6 MUSD
1.0e-9 TUSD
/ foot
Median Estimate (USD): 1.50150 centUSD
0.0015 kUSD
1.5e-6 MUSD
1.5e-9 TUSD
/ foot
High-End Estimate (USD): 3.00300 centUSD
0.003 kUSD
3.0e-6 MUSD
3.0e-9 TUSD
/ foot
Image Logs:
Well logging techniques which create images of the inside of a borehole. A 360° view camera is used that can be lowered into a borehole via logging cable. The camera’s purpose is to provide live images of the borehole walls.
Other definitions:Wikipedia Reegle

Imaging the interior of a borehole is an important well logging technique for conceptualizing the lithology, structure, and wall strength of the borehole. The most straight forward instrument for imaging the borehole is the optical televiewer. An optical televiewer provides continuous 360° views of the inside of a well. As the instrument is lowered into the well the televiewer provides an image on a computer screen of the inside of the well. Fractures can usually be identified with the optical televiewer and the instrument is very useful for looking at the composition and orientation of lithological and structural features that the well passes through. If the well walls are dark colored, coated with material, or the water is cloudy the optical televiewer may not be useful; the alternative instrument used is the acoustic televiewer.[1] Well images are taken in 360° and normally displayed on a screen or printed out making the cylinder shape of the inside of the well a flat image. Computer programs have been developed to show and manipulate the images in a 3D cylindrical shape as if looking at a virtual core sample.
Use in Geothermal Exploration
Optical images are used for direct viewing of the character and relation between lithology, fractures, foliation, and bedding down hole. Borehole wall imaging also provides useful information for geophysical logs, core sampling, water quality data, and flow meter data.[1] For geothermal applications the camera’s electronics and housing need to be specially designed to withstand extreme temperatures and pressures. Image logs are used in geothermal wells to analyze the stability of the borehole walls and the structures the borehole passes through. Faults and fractures can be identified and locations of inflow and outflow. Image logs are routinely used during well logging operations.

Field Procedures
Borehole imaging devices are lowered downhole via wireline cable. Normally all the equipment needed is transported to the site by a logging vehicle. The Optical televiewer is connected to the logging cable and lowered down hole. Images can be seen live on a screen in the logging vehicle.

Optical televiewer[2]

Data Access and Acquisition
An example of well log images from an Optical Televiewer; (left) a flat 360° view; (right) 180° virtual core view.

Best Practices
An optical televiewer is best when the data is used in conjunction with acoustic televiewer data.[1]
Potential Pitfalls
Borehole water may be cloudy; borehole walls may be black or coated with material causing poor image quality.

  1. 1.0 1.1 1.2 John H. Williams,Carole D. Johnson. 2000. Borehole-Wall Imaging with Acoustic and Optical Televiewers for Fractured-Bedrock Aquifer Investigations. In: Seventh International Symposium on Borehole Geophysics for Minerals, Geotechnical, and Groundwater Applications; 2000/10/01; Houston, Texas. Houston, Texas: N/A; p. 43-53
  2. Directional Surveying Specialists. Digital Surveying Directional Surveying Specialists [Internet]. 2012. [cited 2013/10/08]. Available from:

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