“We see a growing demand for flexible pipelines capable of operating at high CO2 pressures. This demand is driven partly by high pressure reservoirs with a high CO2 content and partly by a growing interest in injection of CO2-rich fluids into reservoirs. This has spurred a current cooperation with CERE researchers,” explains Dr. Jacob Sonne, NOV Flexibles.
Permeation of CO2 from inside the pipeline into the surrounding polymer layers – which give the pipeline its flexibility – cannot be avoided. This permeation is taken into account when selecting steel grades for a specific pipe to ensure safe operation through the entire pipeline lifetime.
Currently, exploration off the Brazilian and Western African coasts go as deep as 2.5 km below the ocean surface. As could be expected, the high pressures involved at such depths challenge pipeline suppliers. When NOV Flexibles began measuring the permeability at high pressures, the results confirmed their suspicions.
“We have seen in the experiments that the measured permeation rate in a pipe containing CO2 at 320 bar at 94 °C does not fully match the calculated value when the permeabilities are assumed independent of pressure. Further, the measured permeabilities do not lie on a straight line in an Arrhenius plot as is often assumed,” says Jacob Sonne.
Following the joint experiments, NOV has revised its models for permeability. The resulting permeabilities agree with the measured values. Cooperation continues.
“We always need to document the permeability properties of our pipes as they are typically designed for 20-30 years without any maintenance. If we don’t provide this documentation we don’t have any customers. But there is also a more positive angle to the tests we are doing in cooperation with CERE. A deep understanding of the mechanisms involved will hopefully allow us to design better and cheaper pipelines, thereby obtaining a competitive advantage,” says Jacob Sonne.
He attends his second CERE Discussion Meeting.
“The first time was a few years back. It is a nice opportunity for stepping back a bit from the daily tasks and have a chat with scientists and people from other companies. I get pointers to various trends. Although some presentations are quite far from my own field of work, I find it interesting to hear what others are doing. Still, I think some of the presenters could be clearer in explaining the relevance of their projects. I could probably have done a better job myself in my own presentation. We love to demonstrate our clever equations but tend to forget that’s not what most people want to hear!”