What are the political problems with crude oil?

People fought for Britain when we colonised every African country, they never had "CRUDE OIL".But Britain wanted it so much, that they tried to find some .When scientist found out that it is a non-renewable source meaning it can not be brought back when used and it is made out of dead plants and animals, more of it was in demand because we needed more of it to what we had thought, Crude Oil was then in bigger demand which made it hard for us to gain some.