Blue Stream: The world's Most Difficult Pipeline Installation

International pipeline contractors are playing key roles In constructing some of the most sophisticated pipelines in the world. In recent months, they have completed the world's most difficult pipeline construction ever undertaken in terms of water depth and environment and set a record for installing the longest subsea pipeline in Australia.

Words like innovative technology and state-of-the-art capabilities often come up when discussions turn to Saipem. Although the company's expertise extends into land and offshore drilling, construction of offshoreproduction systems, petrochemical plants and the laying of cross countrypipelines, a significant amount of engineering expertise is spent to solve pipelay problems in the deepwater offshore environment.

For example, the company recently completed the installation of two 24-inch diameter pipelines from Dzhubga on the Russian coast to Samsun, Turkey. The Black Sea crossing was by far the most challenging aspect of the entire 777-mile on and offshore Blue Stream Pipeline project. Along the 236-mile subsea route, the two pipelines descend to a record depth of nearly 7,060 feet.

Construction of Blue Stream project, which carries a price tag in the $3 billion range, was started in spring 2001, by the Turkish company BOTAS and Russia's Stroitransgas. Construction of the 319-mile Turkish onshore section and the 222-mile Russian portion, which includes compressor stations and underground storage facilities, was completed in September 2002.

Like everything else associated with the Blue Stream project, mobilization of Saipem's semi-submersible heavy-lift pipelay vessel, Saipem 7000, that installed the deepwater portion of the pipeline, required special planning. In preparation for the Black Sea crossing, two massive cranes on the ship's deck had to be lowered and the vessel's pipe lay tower dismantled and reinstalled. Also, before the massive vessel could traverse under Istanbul's two suspension bridges and up the Bosporus Strait to the Black Sea, it had to take on ballast until it reached 95 feet of draft in order to pass under the first of the two bridges.

In February 2002, the Saipem 7000 completed laying the first of the two subsea lines, with work on the second completed in June. Considered the most difficult pipeline construction project ever undertaken, along the 236-mile subsea route, the pipelines descend to a record depth of nearly 7,060 feet and had to be installed in steep and irregular seabed areas off the coast of both Russia and Turkey. Once installed, the twin pipelineswould be exposed to highly corrosive hydrogen sulfide. Finding the right pipe for the harsh environment required several years of research and numerous materials trials. The ultra deepwater and highly corrosive marine environment resulted in the selection of a highly resistant steel alloy API X65 flexible pipe with a triple layer of 4mm-thick polypropylene factory applied coating to withstanding high temperature and offering chemical resistance properties.

Several other products were developed to provide pipeline protection in the unique environment, including the world's first cross linked polypropylene, heat shrinkable sleeve to provide joint protection for the compressor station on the Russian side, and at onshore points where the on and offshore pipelines are joined.

J-Lay Installation

The benefit of many years of experience on every continent laying pipe in deep waters, put Saipem in the unique position of being the only international operator currently capable of tackling the installation of subseapipelines in more than 7,000 feet of water.

The J-lay pipelay technique used to install the dual subsea lines is specifically designed to minimize stress on the pipe. Once launched from the Saipem 7000, the pipe sinks under its own weight. Once on the seabed it must withstand significant currents, and in the case of subsea earthquakes, offer enough elasticity to absorb any resulting shocks.

The Russian seabed region posed some specific challenges. Not only is it an area of active seismic activity, the seabed is full of canyons, forcing the pipeline to follow an oblique route. To ensure precise installation of the pipeline on the seabed, the Saipem 7000 relied on its dynamic positioning system to maintain the vessel's position and allow pipelaying in up to Force 6 seas.

Russia is scheduled to deliver 70.6 Bcf of natural gas to Turkey via the pipeline this year. From 2003 to 2009, Russia will increase deliveries each year, with the pipeline reaching peak capacity of 565 Bcf/year in 2009.

Duke Energy International (DEI) recently inaugurated the Tasmanian Gas Pipeline, which includes Australia's longest subsea pipeline project. The new pipeline was specifically constructed to bring natural gas to the island state of Tasmania and connects it to Australia's growing natural gas network.

The US$246 million (A$440 million) project includes 443 miles of subsea and underground pipeline and the conversion of the Bell Bay Power Station on Tasmania to natural gas. The project will provide a much-needed energy alternative for Australia's last state to receive natural gas.

DEI President and CEO Richard McGee said the project completion marked an important international milestone for DEI.

"The Tasmanian Gas Pipeline delivers on a promise DEI made just a few short years ago to bring a new, competitive and reliable energy supply to Tasmania to fuel industrial growth and spur long-term employment opportunities in the state," McGee said. "In four years, DEI has taken the project from pipe dream to construction reality. We've invested in expanding Australia's energy market, creating a new market in Tasmania and enhancing trading opportunities nationally.

The new pipeline is made up of on and offshore segments. It starts at Longford in Victoria and travels 13.6 miles to the Victorian coastline at Seaspray. From there, it stretches 187.6 miles across Bass Strait, coming ashore at Five Mile Bluff, northeast of George Town.

The onshore route, 235.5 miles, travels from Bell Bay and splits at Westwood, a junction point just west of Launceston. The northern pipeline extension is to Port Latta in northwest Tasmania, and the southernpipeline extension is to Bridgewater, on the outskirts of Hobart.

Bass Strait Construction

Allseas Group S.A., the Swiss-based company that installed the pipeline in Bass Strait, is one of the world's leading offshore pipelay and subsea construction companies. To carry out the installation, the company mobilized its pipelay vessel Lorelay from the U.S. Gulf of Mexico.

DEI Project Manager Carl Fisher said the pipelaying process used in Bass Strait involved a number of steps. First, coated pipe was loaded onto vessels that transported it out to the Lorelay. Each steel pipe joint measured 39.3 feet in length and was coated with up to 80 mm of concrete. Once the pipe was aboard the Lorelay, crews relied on four Phoenix semi-automatic welding machines to weld the pipe joints together before ultrasonic testing and coating was carried out.

"As the Lorelay moved forward," he said, "the pipe string was laid on the seabed." The vessel is capable of laying around 2.5 miles of pipe a day, and operating 24 hours a day, depending on the weather and other factors."

In late August, Fisher said the Bass Strait portion was complete and connected at each end to the onshore pipe. Extensive testing of the line was also carried out to ready it for natural gas.

Onshore Construction

In discussing construction of the onshore portion of the pipeline, Fisher noted that a number of contractors were responsible for building this segment which extends from Bell Bay to Port Latta in the northwest and from Bell Bay to Hobart in the south of the state.

A contract to construct the 149-mile Five Mile Bluff to Port Latta (Stages 1 and 2) portion in Tasmania was won by McConnell Dowell Constructors (Australia) Pty Ltd.

Construction of the 102-mile Westwood to Bridgewater (Stage 3) portion in Tasmania was awarded to Nacap Australia Pty Ltd.

Fisher said that the onshore portion of the project was buried at varying depths, depending on land use and other factors such as proximity to existing building and cities. For river and roadway crossings on the project, contractors relied on several methods. Horizontal directional drills (HDD) were used to make major roadway and large and sensitive water crossings, while boring and open cut were used for more traditional crossings.

A team of eight DEI environmental specialists was charged with rehab and revegetation on the project, which involved collecting thousands of seeds in bush areas and establishing more than 20,000 plants and shrubs which were grown in several Tasmanian nurseries.

Record Setting

River Crossing

In addition to completing drills at Five Mile Bluff and under rivers in northern Tasmania, an Australian record was achieved when McConnell Dowell and its subcontractor, Stockton AJ Lucas Joint Venture, a drilling company owned by McConnell Dowell and AJ Lucas, successfully completed the country's longest HDD beneath the Tamar River.

The 6,712-foot curved crossing "punched" through at Rowella on the west bank of the Tamar River on March 22 precisely at the designated exit point. The curved drill reached 282 feet beneath the bed of the river.

Fisher said the successful Tamar River crossing was a significant achievement and set an HDD length record in Australia. An additional 11 rivers in northern Tasmania were crossed using HDD. In all, Stockton-Lucas completed 12 major river crossing in just seven weeks using four drilling rigs.

At the peak of construction, 1,018 people were working on and offshore to complete the project.

Safety

Now completed, the pipeline is being controlled and monitored 24 hours a day via a SCADA system. System features include an automatic alarm system to alert pipeline controllers to any abnormal operating conditions on the line

Sumber : Tubb, Rita. "Blue Stream: The world's Most Difficult Pipeline Installation". 29 Januari 2014. http://search.proquest.com/docview/197495562?accountid=31562