Not everyone is aware that the NCS conceals the world’s largest fully integrated pipeline network for transporting natural gas. The system linking producing fields, process plants and terminals represents one of the finest examples of Norwegian engineering skills and creates huge value for the country.
But how is this value actually created?
Not everyone is aware that the NCS conceals the world’s largest fully integrated pipeline network for transporting natural gas. The system linking producing fields, process plants and terminals represents one of the finest examples of Norwegian engineering skills and creates huge value for the country.
But how is this value actually created?
Many believe that gas is pumped up from below ground, but that is not entirely correct.
Gas reservoirs often have a natural overpressure, and their contents flow out under their own force once the overlying rock has been penetrated.
That is the case to start with, at least. As this driving force gradually declines, water can be pumped down into the reservoir to provide pressure support.
For the gas to flow from the offshore field to the process plant on land, however, it needs a little mechanical support. Pressure is again the key.
Big compressors are used to raise the pressure of the gas in order to drive it through the
pipeline. Its speed varies with pressure and temperature, but will always be highest at the end
of the pipeline where the pressure is lowest.
To convey some sense of the journey time, a gas molecule from Norne – the northernmost field in the pipeline network – can be said to take about five days to reach Germany. That is a distance of 1 480 kilometres, one of the longest runs in the system.
About 30 per cent of the gas brought up is sent directly from producing fields to receiving
terminals. The rest must first pass through a facility on land where this “rich” gas is processed.
A separation plant removes the heavier components, known as natural gas liquids (NGL). These can be sent in turn to a fractionation unit and split into such products as ethane, propane, normal butane, isobutane and naphtha.
The remaining “dry” gas – largely methane – is then piped to continental Europe or the UK, again with the aid of large compressors.
Land-based terminals in Britain and the European mainland are the last stop in Gassco’s pipeline network. These perform a final quality check before the consumer-ready gas flows on to the end user. But Gassco’s job is done once the gas leaves the terminal.
