That could be the explanation, many of these refineries have been attacked multiple times, and I suppose that's because Russians have had them at least partially up an running again.
But there are some parts AFAIK that are very hard to replace and takes up to a year to repair. So the 20% could be facilities that are down for at least several months.

[–] Treczoks@lemmy.world 3 points 5 months ago

Yep. It really depends on if you have to replace some basic hardware like pipes, tanks, and valves that you can do with sheet metal and a welding tool, or if they blew up the control center with the computers and the specialized hardware. Or maybe some of the specialized pumps and valves. Those are expensive, and so nobody has large quantities lying around.

When the Russians hit the Ukrainian power grid, the Ukrainians can get replacement parts from all over Europe and the rest of the world. But Russia has the problem that those parts are high up on the embargo lists, so they have to get either Chinese parts (which may need modifications on them or the controlling software), or smuggle the original items.