Mark Sumner on September 29, 2022: «This week saw the sabotage of the Nord Stream 1 and Nord Stream 2 gas pipelines. The near-universal conclusion of everyone who has looked into this is simple: Russia did it. But the why of the pipeline bombing is not reassuring.»

This view of things has not changed significantly since then, and the search for a possible motive has so far revealed nothing that would have been generally accepted. Why not start with what is known: the inability of the Russian side to operate and maintain complex systems, be it an army, a nuclear power plant, or in this case a natural gas pipeline?

Operating and maintaining a natural gas pipeline is by no means a trivial matter, which always means a risk of human error, and the hair-raising chain of misconduct that led to the Chernobyl disaster is now known in detail, and there is no need to comment in these pages on the disaster of the Russian army and its fellow combatants in Ukraine. What happened on September 26 off the coast of Denmark and Sweden, however, we will not know for weeks, months or even years, whether this was an accident, an operator error or a terrorist attack, but we can already hypothesize what can be ruled out as improbable: Does human error in the operation and maintenance of the pipeline belong in this category, in the sense of "never attribute to conspiracy that which can be explained by incompetence"?

On June 4, 1989, a devastating railroad accident occurred near the city of Ufa in the southern Ural region. A huge gas explosion occurred on the track of the Trans-Siberian Railway, where two trains were crossing. At least 575 passengers died and over 600 were injured. Passengers of the trains were mainly children on their way from or to vacations.

A liquefied natural gas pipeline running near the railroad track had sprung a leak. The operating personnel noticed a drop in pressure on the pipeline, but did not suspect a leak, but rather the failure of a compressor. They therefore switched on another compressor and thus increased the pressure at the leaking point. The leaked gas collected in a depression and exploded just as the two trains crossed. The explosive force of the blast was estimated at hundreds of tons of TNT equivalent.

The pipeline had originally been designed to transport crude oil, but was redesigned to transport liquid natural gas for the Soviet petrochemical industry. In May 1984, the Soviet Ministry of Petroleum had cancelled the installation of an automatic real-time leak detection system...

However, impressive explosions of natural gas pipelines are not limited to the old Soviet Union and the new Russia; they also occur in the USA:

On September 9, 2010, a 30-inch Pacific Gas and Electric Company (PG&E) natural gas pipeline exploded in San Bruno, California, killing 8 people. The explosion resulted in a fireball more than 1,000 feet high and an earthquake measuring 1.1 on the Richter scale.

In the days before the explosion, some residents reported smelling natural gas in the area. At the time of the explosion, the pressure in this section of the pipeline was 26.6 bars. Although this value was 0.8 bar higher than the maximum operating pressure set by PG&E for this section of the pipeline, it was still 1 bar below the maximum allowable value of 27.6 bar.

In January 2011, federal investigators reported finding numerous defective welds in the pipeline. The thickness of the pipes varied, and some welds did not fully penetrate the pipes. As PG&E increased pressure in the pipes to meet growing energy demand, the defective welds weakened further until they eventually failed in one area of the pipeline.

On February 11, 2014, a Hiland gas pipeline exploded south of Tioga, North Dakota. Hiland was busy blowing out methane hydrate plugs, ice-like solids that form from a mixture of water and gas and can block the flow of gas, out of the pipeline.

«Being in the middle of the Oil Patch, we have a department that is accustomed to these kinds of fires», Pederson, spokesman for the firefighters, said. «We know when we can fight them and we know when we should be defensive». Jobs as usual…

A similar incident in Siberia in February 2000: An Gazprom employee attempted to remove a methane hydrate plug by heating an exposed pipe with a flare. Gas pressure from a dissociated hydrate plug rose rapidly, presumably because it was trapped by the plug ends. The pipeline exploded, and the resulting fire killed one man and seriously injured four others.

The release of the methane from the hydrate leads to a strong increase in volume or pressure. These can accelerate the methane hydrate plug in the pipeline: speeds of up to 300 km/h / 185 mi/h have been measured. This in turn can lead to an increase in pressure in the transported natural gas or to a rupture of the pipeline.

Here we actually have two explosions, first purely mechanical due to the pressure increase that caused the pipe to burst, then the escaping gas ignited by the flare. In the following, the term "explosion" will be used for both types of events.

What methane hydrate (methane clathrate) is, how it can come to the formation of a methane hydrate plug and how such a plug can be removed properly will be explained later. Let's first imagine that our water pipe has an ice plug on the wall of the house: Incorrect de-icing, for example with a blowtorch, can cause massive damage and consequences.

The methane hydrate plug hypothesis for the events off the Danish and Swedish coasts comes from LawDog, a U.S. blogger with experience in the oil and gas industry, with the lively participation of a number of commenters with the same professional background. The two threads, nordstream and nordstream II electric instapundit, are casually worded, poorly structured, and are not always factually correct, often contradictory, as far as the facts are concerned, but are worth considering. On the 2000 event in Siberia, a report from the working world, in his words:

Another fun thing that occurs to usually-intelligent people is to «gently warm the area of pipe where the plug is».

Don’t do this. Methane hydrates disassociate really, really rapidly in the presence of heat. A pocket of gas will form somewhere inside the plug, next to the pipe wall, and the massive, localised pressure increase will rupture the pipe, spilling vapourised natural gas all over your heat source.

Funny enough, this actually happened in Siberia in 2000. Pipeline got a nice-sized hydrate plug, and the muckity-mucks at Gazprom got annoyed at how long it was taking to deal with it. Lot’s of yelling, and the Ops guy sent Some Random Schmuck down to the site of the plug with a butane torch, and orders to warm up the pipe to speed up the melting at the plug/pipe interface. Simple, right? There’s no way a butane torch has enough oompf to overcome the thermal mass of a pipeline and burn a hole through the line.

It didn’t. The heat from the torch caused a small pocket of  the hydrate to sublimate into gas, the overpressure involved ruptured the pipe and opened a jet of natural gas right into the flame of the torch. Random Schmuck did not, we think (not sure they found anything of him) survive this experience, nor did several miles of very expensive pipeline.

In the case of possible methane hydrate plugs, for Nord Stream 1 and 2 the situation is quite different: the four strands of the pipeline run under water for a length of 1225 km / 761 mi. Pipelines over dry land have pumping stations at regular intervals to compensate for the loss of pressure as the gas flows through the pipes and to allow diagnostics of the gas flow. In the case of Nord Stream pipelines, diagnostics and maintenance are only possible with the help of inspection and maintenance tools called “pigs” that travel through the pipes with the flow of gas, which presupposes that the gas is flowing: In the case of Nord Stream 1, the flow of gas has been interrupted several times since spring 2021 and stopped completely since August 30, 2022, and in the case of Nord Stream 2, since filling end of December 2021 this has never been the case.

Even under normal conditions not only the operation but also the maintenance of such a plant is a huge challenge, and maintenance requires that the gas flows:

The different inspection tools are inserted into the pipeline via the PIG launchers at the Landfall Facilities Russia (LFFR). Gas is redirected into the launcher and once the pressure behind the tool exceeds the pressure in front of it, it is pushed through the pipeline. Each line is “pigged” individually. The first tool, the gauge PIG takes three-four days to reach Germany. Once it is received and analysed, a cleaning tool is sent through the pipeline – followed if deemed necessary based on the amount of debris and dust it collects – by a second cleaning tool. After that, the inspection tool is sent through the pipe – which takes about nine days. Once received in Germany, the tools are cleaned, maintained and in the case of the inspection tool, the recorded data is recovered and sent to post processing and a three stage analysis.

Conclusion: for a year and a half the gas flow in Nord Stream 1 has been disturbed, and in Nord Stream 2 such a flow has never taken place: no gas flow means no information on the internal condition of the pipeline, no control and no maintenance.

The raw gas as it flows out of a drill hole is not very suitable for longer transport via pipelines; it has to be processed in a complex way. Raw gas can contain hydrogen sulfide (H2S, up to 35%) and carbon dioxide (CO2, up to 10%), both of which are corrosive, as well as nitrogen (up to 15%), water vapor and inert gases such as helium, which have to be extracted for transport and end use.

In the 1930s, the transport of natural gas in high-pressure pipelines gained economic importance. In natural gas pipelines, as the distance from the feed decreases, the temperature drops as the pressure decreases, and an ice-like substance was found clogging the pipelines in such sections. In 1934, methane was shown to form methane hydrate with water present in the natural gas stream that clogged the pipelines, not ice as originally thought.

This discovery triggered a new phase of methane hydrate research, as methane hydrate plugs in natural gas pipelines were problematic for the natural gas industry, especially for the extraction of raw gas at the wellbore, and caused economic losses. The associated problems and accidents led to a variety of research activities aimed at preventing the formation of methane hydrate when handling natural gas, but this can only be done to a limited extent and the methods to remove such plugs are always with the associated warnings:

Hydrate-plug dissociation should always be done slowly and with great care. Rules-of thumb for safe hydrate-plug removal may be summarized as:

LawDog's thesis, animatedly discussed, in a nutshell: The two strings of Nord Stream 1 and the one of Nord Stream 2 have been destroyed by improper actions on the side of Vyborg and Ust-Luga by the Russian operators, with the attempt to remove methane hydrate plugs from one side as the most likely hypothesis. After the blow up with the first two pipelines, the operators later tried the same thing a second time without success, this time with the first strand of Nord Stream 2, then they lost hope of being able to solve the problem, and the second strand, which never had been operating, survived.

If the cause of the explosions is bad decisions, then the results are not random: the same bad decisions should be expected to give the same bad results. Same conditions, same people making the same bad decisions.

The odds of an accident occurring within a relatively short period in the two seperate pipes are not low if the same stupid things are done at the same time to both pipelines.

There is no reason why there should not be multiple hydrate plugs before the first explosion: if the conditions are right for one plug, it’s highly likely that the same conditions can have the same results at multiple points.

Comments by PeterW on LawDog's blog

When the submarine Kursk ran aground in the Barents Sea on August 12, 2000, speculation quickly turned to the possibility that other ships were in the vicinity, as is repeatedly put forward as an argument for the events off the Danish and Swedish coasts. The hypothesis presented here does without this commonplace. In LawDog's words:

In my experience when anything involving energy-industry hydrocarbons explodes… well, sabotage isn’t the first thing that comes to mind. And honestly, when it comes to a pipeline running natural gas under Russian (non)maintenance, an explosion means that it’s Tuesday. Or Friday. Or another day of the week ending in “y”.