Today Russia announced that all payments for its natural gas...

Today Russia announced that all payments for its natural gas into Europe will need to be payed in Roubles.
This move is especially targeted at countries that have imposed sanctions on Russia and deemed to be "unfriendly"
The Rouble to USD is back up and close to the level it was at prior to the invasion.
If nations fail to pay in Roubles, which many are signaling they will, their gas supply will be shut off according to a press release made by Putin yesterday.
This move, if they obeyed, will strengthen the Russian currency and reduce some of the pressure from sanctions.

We may see high instability in gas prices in the coming weeks since western nations, with US pressure, will not be eager to concede to these demands with Russia still very much involved in Ukraine. It would be a massive sign of western weakness to Putin, who would seek to further capitalize on it. He is basically demanding that all buyers of their natural gas open bank accounts inside of Russia and send their funds there to be converted to Roubles. This would open up their funds to seizure the same way Russian funds were seized in overseas bank accounts. There may not be any reason for Russia to seize these funds but it does ultimately put the power in their hands.

German Chancellor Olaf Scholz has signaled that their current contracts stipulate payment in either Euros or USD and that "it will stay that way".
Basically if Roubles become the base currency here it takes away the strength of the US NATO global dollar standard. It is Russia's game of sanctions. One wonders what business US dollars have in transactions between Germany, France and Russia anyway?
The demand to pay in Roubles has so far been rejected by the major gas buying nations including Germany, France and Italy, labeling it as blackmail.

The possibility that Germany refuses to pay in Roubles, and has its gas supplies cut is very real. Germany is already seeking alternative gas supplies from the US and has only continued to buy from Russia out of necessity. This is ironic considering they cancelled the NORD stream 2 pipeline a few weeks ago (with US pressure) which was designed to strengthen German/Russian gas trade.

Natural gas and coal are integral to energy supply because they can both be used in power generation through power plants (unlike brent and crude which accounts for a marginal percentage of base electricity generation), a rise in price of one will mean a rise in price for the other. It is very likely that we will see coal prices above US $300 per ton this month if noone concedes to Russias demand. If gas is shut off it will have an enormous economic impact on both buyer and seller, but more so on the buyer as some industry will be forced to close due to the shortage. Job losses will be huge across the continent.

In 2020, 12% of German electricity production was from natural gas (55% of which they bought from Russia). This has been increasing yearly as Germany has been trying to shift its economy to more environmentally friendly sources of power, natural gas being one of them. German industry as a whole will suffer if this is shut off since industry is the primary consumer of power.

Key industries that need natural gas for processes other than power are,
1 - non-ferrous metals (e.g. aluminium, copper, zinc, tin)
2 - chemicals and polymers (e.g. fertilisers, antifreeze)
3 - non-metallic mineral products (e.g. glass, ceramics, cement, bricks)
4 - plastic packaging for foods and beverages.
5 - Gas is also needed in food preparation and processing, fermentation and brewing

Based on each sector listed above, below is the size of each sector in Germany alone.
1 - 660 companies and 109,102 employees. In 2013, this sector generated total sales of EUR 45.6 billion.
2 - With a 2020 turnover of €190.6 billion, chemicals and pharmaceuticals are the third-largest industry in Germany, behind only automotive and machinery and equipment. Turnover €190.6 billion, Capital spending €8.4 billion, Direct employment 464,437, Number of companies 2,061, R & D investment €13.7 billion.
3 - Market Size: €6bn, Number of Businesses: 353, Industry Employment: 20,884.
4 - no data found
5 - no data found

Russia may be forced to plug up their wells or let it flow onto the ground in case of a mass boycott of their gas. This will further cement high gas prices. Gas wells have to be continually operational, plugging and unplugging wells is costly and takes time.