The intersect method was recently used to directionally drill a 1,110-m section of 42-in. gas line under the Peace River for the North Central Corridor project in northern Alberta, Canada — a project that the HDD contractor says is the largest HDD casing install as well as longest 54-in. diameter install completed in Canada.
The North Central Corridor pipeline, owned by TransCanada Pipelines, consists of 300 km of 42-in. pipe and associated ground facilities. The pipeline — which will transport sweet natural gas from Manning, north of Peace River to Wabasca — will connect the northwest portion of the Alberta system at the existing Miekle River compressor station to the northeast portion of the system at the existing Woodenhouse compressor station. The North Central Corridor project is projected to be online and in service by spring 2010.
HDD is being used at various locations along the North Central Corridor route and the 1,110-m segment under the Peace River, just east of Manning, was completed between November 2008 and March 2009.
The general contractor for the project was Louisbourg Pipelines, Nisku, Canada, and the engineering and inspection services for the project was provided by ENTEC Engineering, Calgary, Alberta. HDD contractor Direct Horizontal, based in Edmonton, Alberta, was called on to handle the HDD work. Direct Horizontal —which has a fleet of 10 HDD rigs, including two 1.1 million-lb rigs — has thrived on taking on challenging projects, similar to the Peace River crossing.
“Overall, it was a very difficult project but with the proper planning, it was successful for us and TransCanada. It is the largest diameter pipe over that length installed [using directional drilling] in Canada,” says Dave Fisher, business development for Direct Horizontal Drilling.
This project brought with it several challenging factors for Direct Horizontal, including fierce cold temperatures, remoteness of location and the installation of 84-in. steel casing at the entry and exit pits to combat the gravelly soil conditions. Preplanning for the day the actual drilling began is what made this project successful, Direct Horizontal officials say.
“[The jobsite] was in a remote location in northern Alberta,” explains Fisher, which forced Direct Horizontal to make sure it had enough spare and backup parts for its equipment, as those would not be readily available if needed.
Due to the remoteness of the jobsite location, the project had to be completed in the middle of winter. Not only did crews battle the jobsite logistics but also the subzero temperatures, which dropped to as low as -55 C. Darkness was also a factor, as the area received only about six hours of daylight each day.
Two self-contained, 3,600-sq ft camps were constructed for crewmembers to inhabit, as the project duration lasted four months and crews worked round-the-clock 24/7. Crews — which included 20 crewmembers on each side of the river — also constructed ice roads to get to and from the jobsite, which otherwise was unreachable. Ice roads are constructed by using water trucks to spray water to build up the ice so heavy equipment can drive on them.
“That’s why you have to get in and out of these projects on time or your equipment will being staying there for the year until it freezes up again,” explains Lon Briscoe, director of business development for Direct Horizontal.
But before the pilot bore could be drilled, crews had to install 84-in. steel casing at the entry and exit pits due to the high concentration of gravel on either side of the river. Boring under the river would be through medium-strength bedrock. The casing allows the drill pipe and product pipe to be installed in a stable borehole. Direct Horizontal also had to custom-build all the drive shoes for the casing.
“We sent our guys to the casing, which was a month-long project,” Fisher says. “There’s never been casing of this size installed in Canada before. It was a challenging install because of the size and diameter of the casing, which also kept cracking the drive shoes from the vibration.”
Using a TT Technologies pneumatic hammer, crews hammered in the 84-in. casing into the gravel on the exit side or east side, going to a depth of 50 m at a 15-degree angle. After the excess gravel was telescoped out of the casing, crews slid in 76-in. casing to a depth of 63 m and then finished the installation with 60-in. casing at 89 m. The entry side, or west side, just needed the 76-in. casing, going to a depth of 25 m.
“The casing allowed us to isolate the gravel and allowed us to drill without being impeded with anything,” explains Briscoe. “Gravel makes it difficult, if not impossible, to drill.”
With the casing hammered into the ground, Direct Horizontal could turn to boring the pilot hole. Crews mobilized a 1.1million-lb American Augers rig on the west side of the Peace River, and an 160,000-lb American Augers rig on the east side. Both rigs were custom-built by Direct Horizontal to meet the needs of the tough Canadian winter drilling season — skid-mounted and highly mobile to operate in the cold. The intersect of the 12 ¼-in. pilot bore took about two weeks to complete.
Direct Horizontal completed the back reaming in three passes, using a 30-in. reamer and then a 42-in. and finally a 54-in. reamer. Each reaming pass took approximately two weeks to complete.
“When we did the reaming, we had the 1.1 million-lb rig and the 160,000-lb rig both tied to the drill pipe so the rotary from both rigs could turn the larger hole openers,” explains Fisher. “Both rigs were turning the string of pipe at the same time. The 160,000-lb rig helped to pull the hole opener toward itself and helped with the rotary.”
Crews had the 42-in. steel gas line laid out in one long string on the east side of the river. The string was welded together while the drilling was taking place. The pipe, weighing approximately 1,500 lbs per meter with a total weight of 2 million lbs, was held up during pullback by 12 cranes.
“The cranes held the pipe up in an arch to rope the pipeline into the same angle that we exited the hole at,” Fisher says, noting the pullback, using a maximum pullforce of 200,000 lbs, took about 16 hours to complete.
As part of the pullback, Direct Horizontal ran buoyancy control inside the 42-in. product pipe to keep the pipe from floating to the top or riding the bottom of the hole. “When we pulled the 42-in. line, we had a 32-in. HDPE DR 17 inside it, which had a 4-in. DR 11 plastic pipe inside of it. We filled the 32-in. pipe with water to create neutral buoyancy of the pipe,” Fisher explains. “Once the pullback was finished, we pulled out the 32- and 4-in. lines and we also removed the casing.”
Both Fisher and Briscoe say the company’s experience in this type of project and the pre-planning were key to getting the job done on time. They noted that crews did cut it close to the start of the spring thaw, explaining that crews had to be flown to and from the jobsite in the final days via helicopter as ground travel was too treacherous.
Sharon M. Bueno is managing editor of Trenchless Technology.