Pipeline &
Gas Journal
August 2000 issue:
by Maretta Tubb, Managing Editor
Duke Energy International (DEI) is the builder, owner and operator of the recently completed Eastern Gas Pipeline in Australia. Mainline construction, under the direction of the Transfield, Willbros, Macmahon and Fondside, Joint Venture (TWMF-JV), was completed this month, with gas scheduled to begin flowing to regional New South Wales, Victoria, and the Sydney market in time for the Sydney 2000 Olympics on September 15.
The $450 million, 795-km. (494-mile) pipeline originates in Longford and traverses East Gippsland, close to the towns of Bairnsdale, Orbost and the Cann River, before turning north past Bombala and Cooma. From the eastside of the Snowy Mountain region, it travels northeast to the coast through Nowra, Port Kembla, Wilton and on to Horsley Park to its termination point on the outskirts of Sydney.
The Broken Hill Proprietary Company Limited (BHP) is lead supplier in the contract to supply gas. BHP will source the remainder of the requirements from Japanese pipe mills.
BHP Petroleum and Esso signed a major gas transportation agreement with DEI, making BHP/Esso the foundation shippers on the Eastern Gas Pipeline.
Initially, gas will be delivered to BHP Steel in Port Kembla, Sithe Energy at Smithfield and to retailers at Horsley Park for distribution to households and businesses in the Sydney region. Gas supply to the towns and regions of Bairnsdale, Bombala, Cooma and Nowra will follow after local distribution networks are established. A future connection of the pipeline to a Canberra lateral is also anticipated.
DEI General Manager Mark Landseidel said the construction project was unprecedented in the Australian pipeline industry. The construction required just over 12 months. Work started with three construction crews working with more than 90,000 tons of steel and 47,000 pipe joints.
“From environmental, technical and cultural heritage perspectives, this project has set new standards and we’re very proud of that achievement,” he said.
An example of this is the HDD crossings required on the project. Cherrington Australia was awarded the primary HDD contract to install seven HDD crossings. The contract represents not only the single largest HDD contract awarded in the history of the Australian pipeline industry, two of the crossings set records for the longest ever installed using HDD.
In discussing HDD activity on the project, Cherrington project manager Jim Perry said the original contract called for the HDD on the project to be conducted in about 70 percent rock and 30 percent sand clay formations. Later, changes resulted in crews having to deal with rock about 90 percent of the time and sand clay formations about 10 percent of the time.
Perry also pointed out that even before work got under way, there was no question the project was going to be difficult. Not just in terms of the physical magnitude of the bores, with the Endrick Escarpment and Cataract Rivers to contend with, but with the environmental considerations involved in conducting drilling operations in national parks, state recreational and catchment areas.
Cherrington mobilized two drilling spreads to the project site in 1999. The first was a 120,000 pound rig mobilized to the site in September. The second was a 150,000 pound Cherrington manufactured rig that was shipped from the U.S.
The first record setting HDD crossing required on the project came during the 1,025-meter (3,362 feet) Endrick Escarpment crossing. Perry said the bore traversed through three different rock formations over the length of the bore, ranging from an Ordovician formation consisting of sandstone, slate and shale, to a 300-meter (984 feet) section of Conjola formation. On the final 400 meters (1,312 feet) of the run, Wandrawandian siltstone and the harder Nowra sandstone formation was encountered.
Despite the difficulties the pilot bore presented, the bore surfaced only one-meter (3.2 feet) to the left and two meters (6.5 feet) above the designated target location.
Over the course of the pilot bore, Perry said crews managed to achieve an average production rate of 100 meters (328 feet) per day.
Pipe Stringing/Reaming Operations
In this phase, space proved to be another obstacle. Cherrington and TWM-JV had identified a cable easement as the proposed site to string the pipe for the final line pullback. When the area proved to be too narrow, another site was selected that limited the overall length of the pipe strings to just 85 meters (279 feet). This meant that 11 separate pulls would be required to get the pipe into the hole.
By January, reaming operations for the bore had been completed. And despite Cherrington consulting with a number of experts prior to the project start, they failed to find a reliable tool that could provide predictable, consistent production. Instead, some reamers lost 10 percent of gauge after just 20 meters (66 feet). In the end, sheer perseverance and relying on Cherrington designed reamers proved to be the answer.
Pipe Pull-In
Final pipe pull-in proved to be an undertaking for crews as well. The pullback started Jan. 12 and required almost four days of continuous operations. Perry said it took the combined efforts of the TWMF-JV and Cherrington to pull it off.
TWMF-JV, charged with pipe stringing, welding, x-ray and joint coating on the job averaged spending about 3.5 hours preparing each respective pipe strings.
Once the final line pull-in began it was critical that delays between pipe string pullbacks be kept to a minimum, otherwise the pipe might become stuck in the lower section of the bore hole.
Six days after stringing and pipe pullback operations began, the installation of the Endrick Escarpment was completed, making it the longest 457mm diameter HDD crossing to date in Australia.
In addition to the Endrick Escarpment crossing, Cherrington completed a 600-meter (1,969 feet) crossing under the Illawarra Escarpment that proved to be one of the most difficult construction segments along the pipeline route. Five additional crossings, totaling 2,855 feet, were completed under rivers, creeks and highways.
The final crossing by Cherrington was the most impressive on the project. Measuring 860 meters (2,821-feet), the trajectory of the 660 mm (26-inch) bore, being carried out in rock, drops under a 120-meter (400 feet) deep gorge and then travels back up the other side before surfacing.
Landseidel said, “Never before has a pipeline been built in Australia across such diverse conditions and topography. Terrain along the pipeline route varies from metropolitan roadway, undulating agricultural lands and steep escarpments to swamps, rivers, valleys and dense bush land.
“Our cultural and environmental program is extensive and ongoing, ensuring Australia’s unique habitats are preserved. Aboriginal monitors and archaeologists assisted the company in preserving Aboriginal cultural heritage along the route. The monitors also worked closely with construction crews to ensure culturally significant features were protected throughout the construction process.”
Safety
The pipeline has met and in many instances exceeded stringent Australian safety standards. Built of high quality steel, extensive testing will ensure pipeline integrity. Hydrostatic testing of the line is scheduled prior to commissioning, allowing the project team to check for leaks and faults. During this phase, water will be transported through the line at a minimum of 1.24 times the design pressure.
Once commissioned, the line will be controlled and monitored 24 hours a day via the SCADA (Supervisory Control and Data Acquisition) system. The SCADA system is configured with an automatic alarm system designed to alert pipeline controllers to any abnormal operating condition on the line.
The pipeline is also fitted with ‘smart valves,’ which will automatically shutoff the flow of gas should an incident occur. Maintenance crews located along the route will be responsible for ensuring all aspects of the pipeline are safe and operational.
Landseidel said DEI was setting new standards in construction and environmental management for the pipeline industry.
After an intensive four-year approval process, DEI sought first to select the most appropriate route for the pipeline to minimize impact to the environment. As such, 95 percent of the pipeline route is in previously disturbed lands such as power, telecommunications, road or rail easements or agricultural lands.
Operation of DEI’s Eastern Gas Pipeline, with an initial capacity to transport 65 petrojoles of gas per year, is slated to begin next month.
Landsidel said the pipeline was a vital element in the economic prospect and growth of Australia. “Competitively priced and reliable energy supply is fundamental to the country’s industrial and economic growth. DEI’s visionary Eastern Gas project embraces this challenge.” P&GJ