Gassco: H-7 Bypass Successfully Completed

The H-7 bypass job on the Norpipe gas line in the North Sea was completed during the weekend, with normal transport resuming today – two days ahead of schedule.

Located in the German sector, the H-7 installation is one of two compressor platforms positioned along Norpipe. The other is the B-11 structure. H-7 has not been in use since 1999, and gas has simply passed over it on its way to the Norsea gas terminal at Emden in northern Germany. Work on tying-in a section of pipeline to bypass the redundant platform began on 10 June.


"The whole job has progressed in a good and orderly manner, with no reported health, safety or environmental incidents," said adviser Lars Olav Eide at Norpipe and H-7 operator Gassco. This work was carried out while the Valhall and Ekofisk fields, which feed gas into Norpipe, were both shut down for maintenance. The operation has been very successful and both the fields are back on stream today along the resumption of normal transport through Norpipe.

"We were a bit late in getting going because of a delayed vessel, but were nevertheless finished ahead of schedule," reported Mr. Eide.


In order to tie-in the bypass line, Norpipe was sealed on either side of H-7 with the aid of high-pressure plugs. The pipe was then cut on each side and the new section welded into place. This length of pipeline was laid around the platform during May. Holding back the gas at a pressure of 60 bar while keeping out water once the line has been cut, the plug technology offers substantial savings in time. "We saved about 14 days by keeping the gas in the line under pressure rather than flaring it off," explained Mr. Eide.


Gassco has participated in planning the operation and simulating gas transport, and in coordinating the operation. "Our share of the work aimed at ensuring that execution was as speedy as possible," Mr. Eide reported. "We actually saved almost a day through good planning of gas transport ahead of the shutdown."

Work on the H-7 bypass was carried out together with ConocoPhillips as technical service provider to Gassco.