International oil and gas deals are typically done with USD , so it’s notable that this deal is in euros. Probably more for political than financial reasons.

China is heavily invested in the dollar so it’s in their own interest not to cause too much damage. But if they decided politics was more important (which they’ve been doing a lot lately) then they could cause damage by announcing they were shifting some of their dollar reserves to euros and start dumping some of those treasuries they hold. If they did that in the next couple months then that would take the wind out of the Fed’s sails as they start switch to quantitative tightening as they reduce their balance sheet. China only has about $1 trillion of treasuries, so they don’t have as much ammo as the Fed has, so I think it’s more the announcement of the shift that would cause the most trouble.

The topic of changing the world’s reserve currency is not new. (When was this last a thing?) Over time it does seem likely and perhaps it would ultimately be beneficial for global stability if the global reserves are more diversified.

From Reuters

Russia, China agree 30-year gas deal via new pipeline, to settle in euros

Russia has agreed a 30-year contract to supply gas to China via a new pipeline and will settle the new gas sales in euros, bolstering an energy alliance with Beijing amid Moscow's strained ties with the West over Ukraine and other issues.