Frozen Sand Provides Directional Drilling Challenge

Contractor Installs Radiant Heat System Under Cold Storage Facility
June 2009 Vol. 64 No. 6

The D36x50 Series II was also chosen because the rig carried the right amount (total length) of drill stem and eliminated the need to offload additional rod baskets. In addition, the unit featured a climate controlled cab to protect the operator from the extreme summer heat and humidity common in the Kansas City area during August and cold Midwestern temperatures during December and January.

Huttmann started out using a four inch carbide blade drill head, but soon discovered the drill head was no match for the frozen sand. He ended up using a four inch mud motor, which handled the frozen sand, but in the last third of each bore tore up the roller carbide nubs and thus had to be replaced after every borehole was completed.

Changes while drilling

The drill was set up on the east side of the building with a setback of 10 feet. The operator bored through the frozen sand to a 4 foot by 4 foot concrete tunnel located dead center under the building. Once the bore was completed the crew pulled back a 1.5-inch PVC duct from the tunnel to the outside of the facility. During the pullback a bentonite mixture, similar to grout, was pumped into the borehole.

“On the first few bores we bored through the concrete wall of the tunnel,” says Huttmann. “But we soon discovered a power line ran along the tunnel wall and ended up boring just to the footings. Then we used a concrete saw to cut open the tunnel wall and reach the borehole.”

Once the PVC duct was in place, a ¾ inch rigid steel pipe was inserted into the conduit from the outside of the building towards the tunnel. The pipe was secured to the inside of the tunnel and then the PVC duct was removed. “The bentonite mixture helps hold the steel pipe in place and will enhance the heat dispersion process,” Huttmann explained.

Production varied from day to day depending on the ground conditions.

“When we started, we’d get two to three bores completed in a day,” says Huttmann. “But there were days when we only completed one bore. The frozen sand was so unpredictable.”

That wasn’t the only challenge. While the lines had to be installed at a depth of 24 to 30 inches, the team also had to avoid steel support piers. Each pier was 18 inches in diameter and set 36 inches deep into the ground. The pier was then set on a concrete pad. The team had to know where they were at all times.