The only thing that Russians forget is that even when it comes to oil they can't do shit without western equipment. The first Russian artic platform was 20 years decommissioned Conoco oil platform, most of the drilling in northern Siberia was actually done by western companies, see the associations with BP and Shell, and what is not western is made in South Korea.
As I know, what concerns the oil and resource research is quite good. At least I've heard they got decent specialists. Also, I agree with your general statement that in globalized world you can't do shit alone (works for any country) but situation with Russia is a bit different. This time there is an external reason for that and since Russia becomes more isolated there is no fear of loosing foreign investors because they already lost them due to other reasons. This rule only applies during the times of free trade.
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On the oil extraction business, it is certain that the extraction, processing and even transportation has become a very specialised business. Even large companies depend on a selected group of technologists and know-how companies. This is nothing like we nationalise and next day we just open as usual. And on the financial side, it is pretty much the same, it is not only the huge investments required, it is the ability to manage efficiently those fluxes of money without loosing them to corruption, inexperience and inflated supply-chains.
If the military invasion of Ukraine by Putin's army is an example of how things are managed in his government, I can already tell you there is plenty of GDP to be lost.