I think you are talking about gas and not oil? Europe imports about less than 3 million barrels per day from Russian crude[1], this amount can be compensated by Iranian oil or even allow Venezuela to export oil, also that 3 million barrels out of a total of total 70 million barrels per day will not lead prices to rise from 100 USD to 300 USD.
Do not forget that these prices may be encouraging for shale oil.
With regard to gas, the story is completely different, as is the cost of liquefied gas, establishing stations to receive that gas, and the cost of the story may easily multiply prices several times.
The oil industry in Venezuela is in ruins,due to the "smart management" by the Venezuelan socialists.
It would take years for Venezuela to recover it's oil industry and this would require foreign investments,which is impossible under the Maduro goverment.
Iran is exporting oil mostly for the Asian countries.I don't think that the Iranians would switch to Europe.
Iran has close relationships with Russia and not-so-close relationships with the European Union.
Anyway,I don't believe that the oil prices can hit a range above 150 USD for long time frame.
Anything above 150 USD oil price would be catastrophic for the global economy.