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Detecting Screen Section Of A Potable Well Using Acoustic Televiewer

An old potable water well was abandoned and to be closed. In order to properly close the well, the depth of the screen section inside the well needed to be found out. Due to the cloudy well water, regular tools such as well cameras didn't work. Enviroprobe was called upon for a solution and we decided to use our borehole logging equipment to conduct the investigation and the acoustic televiewer was determined as our primary investigation tool.

Two different sections of the well are clearly observed in the acoustic televiewer log. In the suspected screen section, a distinct “spotty pattern” and narrow linear bands are visible in the data images of both travel time and amplitude. Note that the televiewer relies on built-in 3-axis magnetometers to orient the recorded images with respect to magnetic north but the strong variations of the magnetic field along the depth indicates the well was made of steel from top to bottom. As a result, the orientations of the images are not reliable, and straight linear features on the wall could look like zigzag paths in the data images. The transition zone between the solid steel casing section and screen section is also indicated in the images.

These two different sections can also be identified by observing the optical televiewer log, but only vaguely.

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