Resonant Sonic Drilling
Description
ResonantSonicª Drilling is an innovative tool used to drill wells that are
primarily used for sampling. The ResonantSonic Drilling rig uses a combination
of mechanically generated vibrations and limited rotary power to penetrate the
soil. The drill head, which is attached to the drill pipe, consists of two
counter-rotating, out-of-balance rollers that cause the drill pipe to vibrate.
Resonance occurs when the frequency of the vibrations equals to the natural
frequency of the drill pipe. The resonance and weight of the drill pipe along
with the downward thrust of the drill head permits easier penetration of the
formation, without adding drilling muds or lubricating fluids.
To obtain samples, one of two methods is used. In the first method, a
wire-line is attached to a barrel that rests upon an open-face bit. After
drilling has proceeded far enough that the inner barrel is filled, the wire
pulls up the barrel without pulling the drill pipe out of the hole. In the
second method, the inner-core barrel is attached to a small steel inner rod
that is removed for core retrieval. The drill pipe that remains in the ground
maintains borehole
integrity.
Limitations and Concerns
Heating samples containing volatile
chemical contaminants
is of concern. Because this technology does not use fluids to cool the pipe and
the formation, it can generate temperatures up to 140 degrees Fahrenheit. This
may volatilize VOCs,
affecting the integrity of the sample and posing worker safety issues.
This method may compact subsurface materials, thus restricting the natural
flow of groundwater and soil vapor. This would limit the accuracy of monitoring
wells drilled with this method.
The effectiveness of the system varies with the soil medium being
drilled.
Applicability
ResonantSonic drilling has been used to sample geologic formations ranging
from unconsolidated gravel-rich material to sandstone/shale sequences to
clay-rich glacial till. Continuous samples have been obtained at depths as
great as 550 feet.
Technology Development Status
This technique was developed in the early 1980Õs. Field demonstrations of
the ResonantSonic drilling technology were conducted at the DOE Hanford Site and
at Sandia National Laboratory from 1991 through 1994. The State of California
teamed with DOE on some demonstrations. The technology now is commercially
available.
Web Links
http://www.osti.gov/bridge/servlets/purl/10109181-7jt82E/native/
http://www.osti.gov/bridge/servlets/purl/197854-vN44jw/webviewable/
http://www.osti.gov/bridge/servlets/purl/174672-ozReYL/webviewable/