The rugged eastern slopes of the Canadian Rockies contain vast oil and gas reserves. Feeder and transmission pipelines must often traverse the slopes and canyons formed by glaciers and rivers over many millennia.
The remote location and rugged nature of the terrain presents significant logistical challenges to pipeline and HDD construction. These challenges, teamed with environmental protection measures, require comprehensive construction planning and risk mitigation strategies.
In the Elmworth region of the Foothills near Grande Prairie, Alberta, Canada, producers ConocoPhillips Canada and Shell Canada routinely face these significant challenges. Productive well-sites in the area needed a pipeline to tie in to Conoco’s new production facility. In this case, the proposed Chinook Ridge Pipeline needed to cross the severely sloped valley walls and river banks of the Wapiti River.
Engineering Technology Inc. (Entec) of Calgary was selected by ConocoPhillips Canada and Shell Canada to direct the HDD engineering, design and construction management functions. Entec is a design/engineering firm that specializes in large HDD crossings and has pioneered the implementation of science (annular pressure monitoring, EDRs, advanced guidance systems, etc.) to mitigate risk to the owner and driller in an industry where risk can be virtually unlimited.
Engineering Evaluation of the Proposed Crossing Route
A feasibility study was conducted, commissioning a thorough geotechnical program. During the process of completing the geotechnical investigation, many key elements were identified that would heavily impact the design of a drilling solution. Varying layers of sandstone, clay and shale were encountered along with numerous horizontal fracture planes, underground aquifers and thick gravel overburdens. Other factors included inaccessible river banks, the 2,700-m (nearly 9,000 ft) distance between the top of the banks — the proposed HDD bore needed to traverse from bank to bank — a 350-m total vertical depth requirement and the fact that the drive from one bank to the other takes five hours. It became clear that the Wapiti River Crossing project would be among the most difficult ever attempted, testing the envelope of mechanical and guidance technologies.
Project Execution Plan
Extensive review and debate resulted in the selection of HDD as the solution, as there were few other economically feasible alternatives. Entec, ConocoPhillips and Shell began the work of building the execution plan for construction specifications, risk mitigation, project management and emergency response planning.
Although doable, completing the project with one long bore (2,700 m/9,000 ft) was deemed as extremely risky due to geology. The project was segregated into two intersect bores. Intersecting the bores was required since entry and exit points were going to need casing installation prior to drilling due to the gravelly overburden.
Once the number and location of the bores were identified, the mud plan was devised. Entec views the mud management plan (rheology, viscosity, weights, pressures, velocities, cleaning requirements and volumes, equipment specs, jobsite design, etc.) as a fundamental place to start with the engineering and design of all crossings. Hydraulics modeling was viewed as a key characteristic and control mechanism for both productivity and risk mitigation. With these obvious goals in mind and geotechnical data in hand, targeted weights, volumes, pressures and plasticity were identified and designed. A further step was taken by recommending that the customer require the use of centrifuges in order to keep the mud working as needed in terms of its carrying capability and the plasticity that would need to be maintained.
The specific drill plan designs were completed concurrently with the mud plans. The first drilling program involved a 1,400-plus m (4,700-ft) bore from the flood plain to the top of the southern river bank. Elevation change from the entry point (valley) to the exit point (top of the band) was 260 m. Gravel overburden at entry and exit required the installation of surface casings at both points and necessitated an intersect point nearly 200 m (about 650 ft) above the lower rig. Drilling rigs were specified to require a minimum of a 300,000-plus lb drill on the lower side and a 140,000-lb rig at the top.
The second program required an 800-m (2,700-ft) drill from the flood plain of the river to the top of the north river bank. Drill rigs used for these two bores were American Augers DD330, two DD140s and a Vermeer D330.
A satellite-serviced command and control center was constructed to allow for the collaboration of the various parties, including: Mears (the HDD contractor), Entec’s drilling management team, the ConocoPhillips pipeline construction and Support Team and the Entec Environmental Monitoring Team, including Gardner Lee Ltd. Jarett McInenly of Entec, one of the four principles within the company, took the construction management leadership role.
Due to the difficulty of the bores, the remote location of the site and the scarcity of roads, the project would need to start at the beginning of freeze-up in order to be completed ahead of the spring break-up. This generally offers a three- to five-month construction season, making coordination of mobilization/demobilization critical for project management.
Mobilization commenced at the end of October, as did a blizzard that dropped 4 ft of snow. Once access had been established, jobsite set-up activity commenced: path surveys, installation of surface casings (48 in. telescoped to 36 in.) to bedrock, installation of centralizer casings, set-up of drilling equipment. During the casing installation phase, aquifers, boulders and cobbles presented challenges to the ‘hammering’ and subsequent clean out operations. The longest installation measured 80 m (270 ft).
Commencement of the drilling program brought about the manifestation of the geotechnical investigation. Sticky, swelling clays, unstable shale and the influx of sand and sediments from prolific underground aquifers demanded the constant attention of the drilling fluid management team. Round-the-clock annular pressure monitoring and fluid rheology monitoring were instrumental in successfully meeting the challenge. There were no fracs-to-surface and returns were never lost.
In early January, the two drill strings touched bits on the first program, but it took another three weeks to establish one constant drill string from entry to exit due to pipe, tool and equipment malfunctions. The difficulty of the intersect cannot be understated as it was made at a point nearly 650 ft above the entry rig. The challenge of having this much drill stem above the rig (many skyscrapers are not this tall) are the obvious safety issues, as well as limited steering control, something that must be managed to within inches to successfully meet the intersect requirements
As reaming operations were beginning on the first bore program, it was becoming apparent that the second program would need to be started prior to the completion of the first in order to complete all activities ahead of the spring thaw. Mears mobilized a third and fourth drilling rig and the same support services noted in the first bore were duplicated on the second.
In mid-February, drilling commenced on the 800-m north hill bore finding the same geologic conditions as encountered on the first bore. February also brought about heavy snow and temperatures in the minus 40 C range (which happens to equal minus 40 F). In the late evening of Feb. 19, the intersection of the two boreholes was completed and reaming operations began.
As the end of the construction season approached, the project team was evaluating all options available in order to help expedite completion. Modifications to the product pipe for the 1,400-m drill were undertaken that would reduce the required reamer sizes to one (by removing the concrete coating requirement, the pipe size would be 14 in. rather than 18.5 in.). Mechanical failures, drill string failures and a fishing operation for a broken mud motor were all adding to the complications of an already difficult drilling challenge.
Success arrived during the midnight hour of March 19 as the 800-m north bank program was completed and the 14-in. concrete coated pipeline was pulled into place. On March 21, the 1,400-m section of 14-in. epoxy coated pipeline was pulled in.
Three furious days of activity saw the first bore completed just ahead of the winter thaw. The team included Conoco members Darrel Hubert, Mark Kappelhoff, Ed Connelly, Harv Penner, Garth Davis among others; Scott Brundrit of Shell; and Prime Horizontal for the intersect guidance; and 30 to 40 others who helped onsite. Intensive technical planning, preparation, perseverance and teamwork saw to the successful completion of the Wapiti crossings.
Added Mark Kappelhoff, ConocoPhillips operations engineer, Deep Basin-Elmworth: “Jarett McInenly poured his heart and soul into this critical project that has recently allowed Shell and ConocoPhillips to move large additional [trapped] gas volumes to sales. In the face of multiple expected and unexpected challenges, Jarett consistently displayed a tremendous work ethic and encouraging attitude that was ultimately necessary to successfully complete the project.
“We feel very fortunate to have had Jarett [McInenly’s] talents along with field and office support from both John Jameson and Grant Jameson and the rest of the Entec staff.”