Roll and lock. For any contractor that performs horizontal drilling, it's the last thing they want to happen. 

When loose rock or gravel rolls into the cavity during directional drilling, its spells disaster. The gravel can lock into place around the drill, preventing the tool from moving forward or backward. That means a loss of time and the need to abandon equipment, which can cost thousands of dollars. 

To avoid roll and rock, brothers Don and Ken Shipalesky of D&K Horizontal Drilling, Spruce Grove, Alberta, Canada, decided to incorporate a pipe ramming tool when performing directional drilling bores in rock soils. 

Their idea was to drive a casing, at a predetermined angle, through gravel-ridden earth until it reach a stable soil. This provides a "guaranteed hole," a bore that will not fill-in or erode. 

With years of experience in directional drilling as an equipment distributor, Ski Craigmile worked with the Shipalesky brothers to develop this unique combination of trenchless tools. Craigmile is now a representative for TT Technologies Inc., Aurora, IL. 

Recognizing this as a new application for pipe ramming, the three men came up with the term "conductor barrel." 

"Today's drilling rigs can have a hard time with gravel," stated Craigmile. He indicated that conductor barrels are not only important for the initial bore, but also during pull-back. 

The Job 

After performing a half dozen bores of this nature, D&K was now asked to perform a single, 4,500 foot, 22-inch diameter bore beneath a rive in a northeast corner of British Columbia for a large petroleum company. "We worked for them before We had to bid, but other bidders weren't capable of performing the bore," stated Don Shipalesky. Not only would this be one of the largest bores for multiple lines attempted in North America, but the elements were also against them. 

The bore was performed in the dead of winter, with an average daily temperature of minus 31 degree Fahrenheit. Plus, the amount of available daylight was limited from 9 a.m. to around 4 p.m. each day. These two factors severely limited the amount of ramming that could be accomplished each day. 

To obtain the desired depth of 76 feet, the crew would need to ram a total of 330 feet (at 15 degrees) of pipe into the frozen ground. Craigmile was onsite for the ramming portion of the job, bringing a Grundoram Koloss rammer, which had a diameter of 14-inches and air consumption of 700 cfm. 

The Koloss was positioned to perform the installation of casings at a 15 degree angle to accommodate the directional drilling rig. The 60-foot pipe sections had an outside diameter of 24-inches. Attached to the front of the first casing was a "cutting shoe," which facilitated slicing through the difficult soil. 

After each section of pipe was rammed into the soil, the Koloss tool was lifted out of the way for the positioning of the next length of casing. This new pipe was then welded to the back of the installed pipe. "The first three joints went in with no trouble at all. Ramming times were approximately 12 to 16 inches per minute," offered Craigmile. 

About halfway into the installation, the rammer was again removed. But this time, it was to allow crews to clean spoils from inside the conductor barrel with an auger. This was done to check the grade of the bore. Using a computerized level to check the grade, Craigmile found that they were right on track. Based on this information, he decided to continue the bore without the need to stop again to check grade. 

The pipe ramming proceeded until the front pipe had penetrated the soft shale beneath the gravel. Once in the shale, the directional drill would be able to make a "clean start," allowing it to travel beneath the river and exit on the other side. 

At 331 feet, the ramming was complete and the Koloss was removed. The auger was used again to remove the earth from inside the conductor barrel. The entire ramming process was completed in six days. In normal conditions, this amount of pipe installation would take hours instead of days. But the incredible cold kept all movement at a snail's pace. 

In fact, the constant, brutal cold affected all aspects of the job. "We had some freezing problems," said Shipalesky. Fuel tanks had to be carefully monitored to prevent gelling of the diesel fuel. A special additive was regularly added to keep the fuel fluid. Crews were also careful not to expose skin to the air, because frostbite could occur in just seconds. 

Successful Completion  

The ramming was now accomplished. D&K now had their "guaranteed hole," and were ready to complete the installation. 

Because the conductor barrel was extremely secure in the soil, no directional drilling anchors were needed. Two ears were welded onto the exposed conductor barrel, which allowed the attached directional drilling machine to push the full 160,000 pounds without moving. An American Augers DD-160 was used to make the bore. 

Using a 9 7/8-inch bit, Don Shipalesky guided his directional drilling tool down the conductor pipe to the shale. There, Shipalesky proceeded horizontally beneath the frozen river, drilling the pilot bore. The bit was then angled up to exit at the top of the river valley hill. Soil conditions there offered no problems for the bore's exit. Crews then backreamed the pilot bore to 14 inches in diameter. Two more back reams were performed to attain the desired 22-inch tunnel, which would accommodate the lines. 

Plans had been to install three steel lines in the hole, an eight-inch for oil, a six-inch for gas, and a four-inch spare. This was modified for the oil company to simply the eight and six-inch lines. The eight-inch line was designated for natural gas, with the six inch as a spare. In all, D&K spend just under three months to perform the 4,500 foot installation. 

This contractor's innovation provided the solution to the difficult bore entry. D&K Horizontal Drilling was able to lower installation costs as well as limit the disruption to the region's ecosystem. 

Reprinted from Pipeline & Utilities Construction, October 1996