Australian offshore pipelines conquer new waters

Over the last five years, the Australian records for the longest and largest diameter offshore pipelines have been set and broken. The 300 km long Tasmanian natural gas pipeline, completed in 2002, was at the time the longest offshore pipeline on record in Australia. A few years later, it was outdone by the 26 inch diameter, 500 km long Bayu Undan gas export pipeline. In 2003 Woodside Energy completed the installation of its 134 km long and 42 inch diameter second trunkline, the largest diameter offshore hydrocarbon pipeline in Australia to date.

While there have been many new records being made recently, there are likely to be many more as a natural consequence of the resource boom. The development of the vast natural gas fields located around Australia is a major driver of heightened offshore pipeline activity.

Not all offshore pipeline engineering is for the hydrocarbon industry. Outfalls for the disposal of treated domestic or industrial waste regularly present substantial design and construction challenges on par with subsea pipelines. However, in the context of growing demand for energy and natural gas specifically, hydrocarbon pipelines will have the greatest potential for growth.

Challenges in offshore pipeline engineering and construction are numerous. Many of the newly-planned pipelines are in unexplored waters. Extensive seabed surveys are needed to provide the necessary information to enable offshore pipeline engineers to find an appropriate route and design for the infrastructure. Almost everywhere around Australia the ocean conditions are hostile. Extreme tropical cyclones form the basis of the design hydrodynamic loading conditions in Australia’s north. Engineers have been innovative in developing solutions to safeguard the pipelines during such events. Ambient sea-state conditions challenge the construction of pipelines around Australia, in particular along the west and south coast, with the Southern Ocean arguably being the most notorious.

One of the companies which has been at the forefront of some of the most challenging offshore pipeline projects both in Australia and overseas is Perth-based engineering company Atteris Pty Ltd. With their innovative approach to engineering and construction management, Atteris has added value to major projects such as the Trunkline System Expansion Project, Otway Gas Project, Blacktip Gas Project, Tangguh LNG Project, the Gorgon Project, and currently the Pluto LNG Project.

The Gorgon Project is a key example of the types of challenges often associated with offshore pipeline engineering. Located off the northwest coast of Western Australia, the Gorgon gas fields, combined with neighbouring gas fields in the Greater Gorgon area, contain resources of approximately 40 Tcf of gas, Australia’s largest-known undeveloped gas resource.

The project proposal includes:

* Development of the Gorgon and Jansz gas fields involving subsea pipelines to Barrow Island’s western coastline.
* A gas processing facility on Barrow Island consisting of two LNG trains.
* LNG shipping facilities to transport products to international markets.
* Greenhouse gas management via injection of carbon dioxide into deep formations beneath Barrow Island.

Chevron engaged Atteris to assist with conceptual (pre-FEED) engineering including route selection for the nearshore section of the Gas Export Pipeline Systems, and development of a suitable method for the shore crossing construction.

This project has an exceptional shore crossing on a global scale in view of the numbers of pipelines to be installed, the remote location, and the value of the shoreline from an environmental point of view.

The study commenced with a review of environmental sensitivities, geotechnical conditions, metocean conditions, and nearshore bathymetry of Barrow Island’s coastline. The subsequent comparison of construction techniques indicated that horizontal directional drilling is the preferred solution providing the least environmental impact, shortest construction duration, acceptable cost, and manageable execution risk.

The Gorgon Joint Venturers are currently looking to finalise the details of government environmental approval so that project value can be fully defined. Given the over-heated global construction market, the joint venturers are also undertaking optimisation and evaluation studies to ensure the project is internationally competitive and will then look to close out associated FEED work in preparation for a final investment decision.

On another project, Woodside Energy engaged Atteris to perform FEED associated with the gas export trunkline system for the Pluto LNG Project.

Atteris’ involvement commenced in 2005 with the provision of support to the Woodside team in two areas of the Pluto project; the export trunkline system route selection particularly in the nearshore area and landfall site selection, and the engineering of the new shipping channel. FEED is scheduled to be complete mid-year and, pending a Final Investment Decision in mid-2007, seabed preparation works are planned to commence in 2008. Pipeline installation is scheduled for 2009 to ensure first gas production by mid-2010.

“We are proud to be involved with such a prestigious project and interact with other reputable engineering companies,” says Atteris Construction Manager Bart Hollemans, who will be tasked with the seabed intervention and nearshore stabilisation construction management. “It provides us with an opportunity to deliver another successful scope”.

Challenges in the pipeline industry will always be numerous. The largest challenge for engineering companies these days is the sourcing and retention of competent engineering professionals. The current global demand for energy is driving a boom. There is much work around, and the pipeline engineering and construction companies are stretched for resources. Nonetheless, Atteris has been able to grow by adopting effective strategies to attract capable engineers. They will be part of a team who specialise in further developing the arteries of our nation’s energy supply, in particular in the more challenging areas.

“We do not live in a perfect world and need to be prepared to deal with that”, says Atteris Managing Director Eric Jas; “It requires flexibility and positive thinking.”

Atteris is currently also involved with several other projects, including two in the Browse Basin and one in North America, and will continue supporting projects using its four key areas of expertise: pipelines, horizontal directional drilling, tunnelling, and dredging.

While there have been many new records being made recently, there are likely to be many more as a natural consequence of the resource boom.

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