A push by the United States to end the war in Ukraine has raised questions about how companies might begin to return to the Russian market and how Europe might re-engage with Moscow, including resuming piped natural gas supplies.
The Nord Stream pipeline across the Baltic Sea to Germany is by far the biggest route, alongside flows via Belarus, Ukraine and Turkey.
Below is a look at the idea of resuming Nord Stream flows:
WHAT IS THE NORD STREAM PIPELINE?
The Nord Stream pipeline is in fact two double pipelines able to deliver 110 billion cubic metres (bcm) of gas to Europe each year, or enough to supply some 26 million homes.
The first pair, Nord Stream 1 (NS1), started operations in 2011 and the second, Nord Stream 2 (NS2), was completed in 2021, but never received an operating permit to begin flows.
Controlled by Russian gas firm Gazprom (GAZP.MM), the project was also backed by large Western energy firms including Shell (SHEL.L), E.ON (EONGn.DE), Uniper (UN0k.DE), Engie (ENGIE.PA), OMV as well as Wintershall Dea (WINT.UL), now owned by Harbour Energy (HBR.L).
WHAT HAPPENED WHEN EXPLOSIONS HIT THE PIPELINE?
One obvious hurdle to resuming supply via Nord Stream is damage caused by explosions in September 2022.
The damage hit both lines of the original pair of pipes and one in the second pair, leaving one line intact. It remains unclear who was responsible for the damage.
Some Western officials have suggested that Moscow blew up its own pipelines, an idea dismissed as "idiotic" by Russian President Vladimir Putin.
Russia has blamed the United States, Britain and Ukraine for the blasts. Those countries have denied involvement.
The broken line of NS2 is estimated to still contain approximately 9-10 million cubic metres of natural gas, while the intact line remains filled with gas.
WHAT ARE NORD STREAM 2's FINANCIAL PROBLEMS?
The second pair of pipes also faces financial trouble, with operator Nord Stream 2 AG, a unit of Russia's Gazprom, under pressure to pay its creditors.
A Swiss court has set a deadline of May 9 for Switzerland-headquartered NS2 AG to both restructure its debts and pay back its small-scale creditors, adding it could declare it bankrupt if this condition was not met.
Russian Foreign Minister Sergei Lavrov said in January that the potential bankruptcy or sale of NS2 AG would amount to "theft".
NS2 AG could not be contacted for comment.
Gazprom did not respond to a request for comment
WHAT IS THE STATUS OF LEGAL CASES?
There are also several ongoing arbitration cases against Gazprom over disruptions to its supply of gas.
Cederic Cremers, executive vice president of integrated gas at Shell, one of the financial backers of the NS2 pipeline, said these cases would need to be resolved in a first step before any considerations around a restart and even then the question was if Europe still wanted the same dependence on Russian gas.
In December, the U.S. administration under then President Joe Biden issued further sanctions on Russia-based entities over their involvement in NS2, including its operator and a Russian insurer that provided insurance to companies involved in the project.
WOULD EUROPE WANT TO BUY RUSSIAN GAS AGAIN?
Another challenge to reopening Nord Stream is that Europe has shifted away from Russian energy supplies since Russia's annexation of Crimea in 2014 and its invasion of Ukraine in 2022 and may not want to shift back.
Although the European Commission has delayed an announcement on a plan to phase out EU reliance on Russian energy, it has said NS2 is not a project of common interest and does not diversify the EU's energy sources.
Germany, previously Europe's biggest buyer of Russian gas, recently reiterated it was not in talks with Moscow over gas supplies.
Most European countries have been seeking out alternative supply including by boosting liquefied natural gas (LNG) imports from the United States, Africa and the Middle East; taking more piped imports from suppliers such as from Norway and Algeria, and increasing renewable energy generation.
