Final report for SNL/NM environmental drilling project Page: 25 of 109
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concentration. This drilling/borehole completion test at SRS was then terminated and the machinery
returned to CMW. Trajectory planning, tracking and plotting for this test was accomplished with the
use of a hand calculator and manually plotting the trajectory. The field mass spectrometer was used
by SNL Materials Center personnel to monitor entry portal vapors during this drilling and casing
activity. Even though the M-Area site had measurable levels of TCE in the soil at the depths being
drilled, no detectable levels above background were detected at the entry portal.
An additional test was performed at the TNX Facility at SRS. This facility is located on a low bluff
along the Savannah River, separated from the river by a marsh area which is a protected wetland.
Concern about possible TCE subsurface contamination at the wetland area was the driving force for
this test. A Jet Trac machine was used to attempt a shallow bore of approximately 300' length. This
test was not successful for two reasons: first, machinery problems; and second, the geologic
formation consisting of fine, wet, running sand that was not compactable. The borehole could not be
stabilized.
2.2.3 Second SRS Field Test
During the fourth quarter of FY 92, the machinery and project personnel from SNL and CMW
returned to SRS for a second attempt to emplace a usable well for the RF soil heating experiment.
This time the X-810 was launched from a shallow pit prepared by SRS approximately 5' (but later
determined to be 2') off line from the first borehole. This launch configuration is shown in Figure 11.
The test plan was to bore a second hole parallel to the first and pull back fiberglass casing provided
by SRS that was environmentally and thermally compatible with the RF heating goals and also had
greater tensile strength than the Teflon and PVC tried in the first hole.
Drill rig stability was greatly improved by using the pit launch technique. As mentioned above, the
location of the new borehole entry portal was not offset from the previous borehole as far as
originally intended. This positional error was due to uncertainty in the exact location of the first
borehole entry, caused by post-test excavation at the site. The result of mispositioning the new hole
was that the boring head and drill string soon drifted into the old borehole. A decision was made to
continue in the old hole and then try to redrill to the exit end and bypass the broken casing remaining
in the old borehole from the first attempts to complete the well. This strategy paid off and redrilling
the exit end resulted in the exit portal being slightly offset from the first exit portal. The X-810 was
again configured with a reamer, pulling plug, and the 3" diameter casing. The entire string of the
new fiberglass casing was successfully installed in approximately four hours. This casing proved to be
strong enough to sustain the drag and bending forces in this installation. The fact that the clay was
wet and slick from the water added during boring/reaming also contributed to the successful
installation. Figures 12 and 13 show the casing installation activities at SRS. Figure 14 shows various
types of casing.
Software newly developed at SNL was used to plan, track, and plot the trajectory for this wellbore
and to make real-time corrections to the trajectory while drilling.
Completion of the well for use by SRS included adding a riser section of casing at the entry and exit
portals to bring the casing to the desired above ground level, swabbing the well to clear out water and
formation mud that had entered the casing during installation via the screen slots, and finally, an
independent survey logging by Sharewell Inc. and SNL to verify the well geometry. This survey
basically confirmed that the data from the less sophisticated onboard steering tool used to guide the
boring head during boring was reasonably accurate. Refer to Appendix A for more detailed
information regarding this test.18
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Wemple, R. P.; Meyer, R. D.; Staller, G. E. & Layne, R. R. Final report for SNL/NM environmental drilling project, report, November 1, 1994; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1280825/m1/25/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.