A massive effort of men, machines, technology and dollars will bring gas from one of the largest fields ever discovered offshore Norway first to shore for processing and then 745 miles (1,200 km) to Easington, UK, where it will meet up to 20% of that nation’s natural gas needs for the next 40 years.

The Langeled pipeline from Nyhamna, Norway to Easington is the longest subsea pipeline in the world.

Ormen Lange also features the biggest deepwater wells in the world, according to operator

Nexan Spiders cleared a path and dug subsea trenches from Ormen Lange to Nyhamna. (Photo courtesy of Norsk Hydro)
Norsk Hydro. Hydro organized and managed the construction phase of the project. It will hand operations over to Shell after the project is commissioned. Shell also drilled the production wells for the field.

The gathering system to get gas and condensate from the subsea reservoir to Nyhamna on the US $10 billion project alone required a massive effort, according to Hydro.

Templates
The company will develop the 25- by 6-mile (40- by 10-km) field using two templates. Those templates determine the drilling positions for the 24 wells that eventually will produce almost 2.5 Bcf/d from reserves of 14.1 Tcf of gas. It’s Norway’s second largest gas field after Troll. It also will produce 50,000 b/d of condensate at peak production.

The templates will rest in 2,789 to 3,609 ft (850 to 1,100 m) of water.
Hydro called it the first large-scale offshore field where the production templates lie at this depth on the ocean floor.

The 100-tonne templates went through rigorous testing procedures at Nyhamna to make sure they could handle production operations. While testing was in progress, crane operators rehearsed the placement on simulators, over and over. If they put it in the wrong place, the company would have to build a replacement template, and the cost to install one template was $21 million.

The installation team used the Heerema Thialf, the world’s largest crane ship for the installation. They carefully lowered the unit to the sea floor. It was so heavy the legs sank
262 ft (80 m) into the sea floor.

With the first template in place in late 2005, the companies drilled the first wells. Plans call for the first eight wells in 2 years. Shell and Hydro will monitor that drilling in The Cave, a surround visualization chamber.

One person compared the operation with a dentist on the tenth floor of a building drilling out a cavity in the mouth of a person on the first floor.

Storrege slide
A subsea landslide off the coast of Norway 8,000 years ago created a tsunami so large that it reached the coast of Scotland. Called the Storrege slide, the movement of that much earth created a rugged series of peaks — some as high as 262 ft (80 m) — and valleys on the sea floor and a 984-ft (300-m) bluff with a 30º to 35º slope in the 74 miles (118 km) between the production templates and Nyhamna.

Hydro had to figure a way to clear a path through that seascape for two 30-in. pipelines and associated umbilicals.

With sea-bottom temperatures at 29ºF (-1.2ºC), the company planned to inject glycol anti-freeze into the condensate-gas-water production stream and bring the whole solution to Nyhamna for separation and to recycle the anti-freeze.

First it used remotely operated vehicles (ROVs) to construct detailed maps and built a 3-D model of the sea floor and the slide. It couldn’t allow long spans of pipe to bridge between peaks in the strong North Sea currents.

It determined a path for the line and recruited Nexan Spiders, remote-controlled excavating machines to dig six trenches 13 ft wide and 13 ft deep (4 m wide and 4 m deep). The longest was 3,281 ft (1,000 m).

The Spiders originally were designed to work onshore in Swiss forests. Nexan had to rework
It took the world’s largest crane barge to lower an Ormen Lange template to the sea floor. (Photo by Mediafota as, courtesy of FMC)
the undercarriage for deepwater dredging. At Ormen Lange, it moved along the seabed on four individually controlled legs shaving peaks and filling valleys.

Jet nozzles on the excavation shovel used high-pressure water to dissolve and remove clay so it could be vacuumed up and sprayed away.

Using a virtual reality model, surface teams were able to manipulate the Spider with 3.9-in. accuracy in muddy water with almost no visibility. The spiders moved some 4,578 cu yards
of earth to prepare for the pipelines and umbilicals.

While one machine cleared a path three similar machines dug the trenches for the pipe and cable.

Hydro brought in the Saipem S7000 and the Allseas Solitaire, two of the biggest pipelay vessels in the world, and set aside a full summer to complete the pipeline installation. That task also needed 11 other specialized vessels and support vessels. The Solitaire, the largest pipelay vessel in the world, started the work. It was capable of welding and deploying 400 sections of pipe a day. The S7000 installed the final 12 miles (20 km) of pipe down the Storegga slide and through deep water to the field template.

Hookup
The team had still more work to do on the project. It had to manufacture and mount and install the pipeline end terminal (PLET) on the drilling template on the sea floor.

Like the template, the PLET was tested and its integrity verified for long-term activity on the sea floor. This also was a no-mistake portion of the job. The large PLET had to be carefully lowered onto the template with the help of ROVs. The ROVs then had to solidly attach the PLET to the template.

Next, the ROVs had to connect pipelines and umbilicals to the PLET while operators at Nyhamna tested the connections to make sure they were leakproof and all systems worked as planned.

The companies built an exact replica of the PLET so installation operators could practice the installation on dry land onshore in Nyhamna.

While experts pieced together the gathering systems, work on other parts of the Ormen Lange project continued. That included the pipeline to the United Kingdom and a massive plant at Nyhamna that could separate water, condensate, glycol and natural gas.

The plant will clean the water so it can be pumped into the sea. It will pipe the condensate to storage where it will wait for tankers to haul it away. It will recycle the glycol and return it to the template for injection into the production stream. It will dry the gas for its long trip to Easington.

At its peak, the project employed some 3,500 people.