I am unconvinced by the idea that high oil prices were good for the Soviets. It may be correct, but, there are various ways that high oil prices also hurt the Soviets.
High oil prices encouraged the Soviets to invest more in their oil extraction industries, when the most efficient thing would have been to do as the West did, and import oil. The Siberian oil was difficult to get to, requiring expensive investments in infrastructure and extensive imports of Western technology (like the large diameter oil pipes, imported if memory serves from the UK, in any case, the Soviets simply didn't have any factories capable of producing pipes in that diameter). Of course, at the time oil was starting to flow through the expensive investments in the mid-80s, the oil price was starting to collapse.
And of course, resources used to develop distant oil and gas reserves in Siberia weren't being used to improve the Soviet electronics industry or the Soviet steel industry or improve the quality of Soviet cars etc.
High oil prices in the West encouraged the Soviets to limit their own oil consumption and the oil consumption of their allies and preferentially export to the West. Coal is a less efficient fuel than oil and gas, so keeping the Eastern block running on less efficient coal for the overwhelming majority of its energy was keeping overall efficiency down and therefore repressing economic productivity. The Soviets were also under-pricing coal (for political reasons) so lower oil prices in the West doesn't push the Soviets to use oil as much as optimally, but it does help. As such, lower oil prices in the West might mean that the Soviets and their allies manage to enjoy greater productivity gains during the 70s, meaning growth slows relative to their performance in the 60s, but not the humiliatingly poor performance of OTL's 70s.
Sudden economic collapses are much more dangerous than slow declines. Especially when one is in debt. The subsidy of high oil prices in the West allowed the Soviets to put off reforms in more fundamental sectors of their economy like the steel industry (which was being clobbered by the exhaustion of coal and iron ore mines in the west of the USSR) while importing and borrowing heavily from the West (or at least, heavily compared to previous levels of trade and borrowing - contrary to popular mythology, the Soviets were never an autarky), then suddenly the oil price goes down and the Soviets had to confront all the accumulated problems at once. With lower prices, the Soviets have to address their more fundamental problems over the course of the 70s (something that theoretically at least they can do - the Soviets had been tackling fundamental issues as serious in the 60s as well and they didn't collapse in that decade) and they don't have the ability to quickly ramp up their imports and borrowing, since without oil they need to develop their industrial exports, which means improved quality, which takes time.
So high prices in oil caused a bubble economy that allowed the Soviets to avoid making hard decisions until it was very late in the day and thus very difficult.
Had oil prices been lower, the Soviets may still have made poor decisions, and thus collapsed earlier, but I think this is a lower probability outcome.
Now, interestingly, had the Soviets still collapsed with low oil prices, (a) they'd have invested less in oil production and (b) 1981 is before Siberia's oil and gas developments were on-stream even with OTL's rush to develop them and a collapse in the middle of building such a major infrastructure project would basically mean it would never be completed - or at least it would be put off for a generation. As such, the post Soviet regime (regimes?) wouldn't be able to use oil and gas as political weapons the way Putin's regime has.
Well, Stalin completely botching his post WW2 diplomacy was probably worse. The Cold War was a disaster for the development of the USSR in my view. While it's hard to avoid a rivalry between the extremely assertive post-WW2 US and the very incompatible economy of the USSR, a much more friendly rivalry is, in my view, possible. Freer trade, less military spending and less ideology warping economic decisions on both sides of the iron curtain would have been good, and it would have been especially good for the Soviets.
But ya, I agree that the discovery and decision to exploit Siberia's oil and gas was poorly timed.
fasquardon