A team of researchers from the French organisation Science-SAVED (Scientific Analysis Vitalises Enterprise Development) and Research Neutron Source Heinz Maier-Leibnitz (FRM II) at the Technical University of Munich (TUM) developed a novel way to keep underwater oil and gas pipelines clean and flowing, according to a study published in the journal Nondestructive Testing and Evaluation (1).
Some oil and gas pipelines can stretch for thousands of kilometres underwater. The Nord Stream pipelines, for example, transport these sources of energy over long distances underwater to storage and production facilities on land.
Under certain conditions, the contents in the pipelines can become very viscous and even form solid masses clogging the pipes. One example involves solid hydrates formed from gas and water, which can happen in particular when the mixture cools down to extremely low temperatures felt on the seabed. As a result, it’s common for these pipes to get blocked.
When this happens, cleaning operations are not easy. In fact, for the blockage to be fixed, engineers first need to find the right section of the pipeline, which is virtually impossible without destroying the pipe.
To date, the most common way to find these blockages on land involves imaging cameras and gamma rays, but this approach doesn’t work underwater. Ultrasound is an option, but blockages can only be detected within a very close range. This is virtually impossible to achieve as pipelines can be laid up to 2000 meters deep and are covered by sand and silt.
The team involved in this work believes the best solution for this problem involves neutrons. This would be a non-contact, non-destructive and reliable way despite thick pipeline walls. “Neutrons are the perfect probe for the task at hand,” said Dr. Sophie Bouat, CEO of Science SAVED. “Using prompt gamma neutron activation analysis, light atoms and hydrogen, in particular, can be detected very precisely.” As the hydrogen content in hydrates is different from oil and gas, it should be possible to detect blockages by measuring hydrogen levels.
A feasibility study conducted in Munich revealed extremely positive results: a sufficiently large number of neutrons can enter the metal walls of the pipelines to detect what’s happening inside, and these measurements can be done underwater. In other words, this approach can be used to separate between the normal flow of oil and gas and blockages.
“Our experiments have shown that we can even distinguish an incipient blockage from a fully developed one,” says Dr. Ralph Gilles from the Research Neutron Source FRM II. “That’s very beneficial because then one can even preventatively heat a pipe segment to melt the blockage before it fully develops.” In practical terms, it’s not difficult to envision a mobile detector with a small neutron source constantly moving along the pipeline, looking for blocks.
(1) Bouat S, Pinier L, Sebastian X, Losko A, Schütz R, Schulz M, Revay Z, Ilic Z, Mauerhofer E, Brückel T & Gilles R (2021) Detection of hydrate plugs inside submarine pipelines using neutrons, Nondestructive Testing and Evaluation, DOI: 10.1080/10589759.2021.1990284