Europe does have petroleum (although technically EU doesn't) both Scotland & Norway have a fair bit

Which is great, except they can't produce much more than they already do, especially Norway. If Norway weren't tapped already, then e.g. Germany would most definitely buy a lot more gas there rather than expensive LNG from the US/Qatar or semi-sanctioned LNG from Russia. But it's simply not possible.

And sure, even Germany has some untapped gas reserves, but besides the environmental hazards through fracking, those reserves are projected to last for a total of 20 years of the current level of consumption in Germany.

If the EU were to stick with its current oil/gas consumption, the vast majority of said oil/gas would necessarily have to be imported from outside the EU.