STABILIZATION OF BOREHOLES DURING GEOPHYSICAL LOGGING

While logging boreholes with very expensive tools, the concern is that the borehole will slough material entrapping the tool. The FLUTe blank liner (i.e., no tubes or other instruments attached) is ideally suited for the support of the borehole while logging tools are run in the hole. The liner is a polyurethane coated nylon fabric. Many logging tools can "see" through the liner. Those that can are the following:

• Gamma
• Neutron moisture
• Acoustic televiewer
• Sonic
• Electric (induction coupled only)
• Temperature
• Radar
• Video (when used with a transparent liner)

The basic Everting Liner Mechanism is described under Methods. See Towing of Logging Tools for the use of liners in carrying sondes through boreholes in any direction, even vertically upward.

The USGS at Storrs, CT has to date done work with logging tools inside liners. The tools which are not compatible with the liner are the flow measurement methods and those requiring contact with the borehole wall. See Characterization of the Formation for the new use of a blank liner to assess the flow paths in the hole during the liner installation. Another more recent form of temperature logging inside a blank liner is of much higher resolution because the liner prevents mixing flow in the hole.

A unique liner material is available which is essentially transparent. This material allows the use of the azimuthal scanning video tool without the risk of hole collapse on the tool.

Another attractive feature of the FLUTe blank liner, in addition to the stabilization of the hole, is that the liner also seals the hole against contaminant spread after the hole is drilled, during the logging procedure, and thereafter, before the hole is instrumented. See Blank Liners for a description of the several installation methods for blank liners.

Liners have been used to tow instruments (e.g., moisture logging tools) into horizontal holes with numerous bends. The instrument is attached to the interior end of the liner. The logging cable is the tether. The liner support of the hole and the ability to tow the tool for long distances makes this an especially attractive application. See Towing of Logging Tools for more information on this application.

For more information about a specific application, contact us at