Are these refinery and oil depot attacks merely small annoyances to Russia or do they significantly impact their economy?
No question they are hurting Russia.
They have gone to rationing.
Russia has won several wars due to the severe winter harming its enemies. Ukraine is turning that against Russia, creating shortages in fuel as they go into winter.
The gasoline shortages have finally hit Moscow this week.
It appears the Ukies got the distillation tower @ the refinery in Ryazan. That’s 5% of Russia’s refining capacity, right there. Distillation tower major rebuilds take a lot of time and money, as it’s a big, complex job, and proper parts are in short supply.
There are a couple ways to look at this. Much of Russia’s refined products are exported, at good (for Russia) profit margins. If you curtail those exports, it forces Putin to wring the money for his war from other sources, like Russian pensions.
If the products for domestic use are curtailed, that causes price increases and local shortages. When a BP refinery in Northern Indiana was flooded by a thunderstorm back on Aug. 18, that caused our 87 octane gas prices to jump by ~ 28 cents, even though we are over 300 miles away, and operations were restored in a few days. (The USA has over 3x the refining capacity of Russia.)
Probably the key concerning Russia is that Ukraine has been gradually increasing the volume of Russian refining production offline (figure taken at any one time, not “cumulative”, as refineries back in operation have to be added back in to get a true picture.) This despite the Ukies having rather limited weaponry to work with. If Ukraine were to suddenly acquire some 30+ y/o US weapons tech to add to their existing weapons, or more capable US weapons themselves, Russia’s refined products supply would be fatally compromised.
You can’t run even a semi-modern country without a good supply of refined products. Without it, Russia would grind to a halt, and I don’t just mean their war effort.