Why do they have such a large population then? Is it truly the oil?
People with lower incomes and standard's of living tend to have more children. This is mainly caused by boredom, lack of work or anything fun to do like in the west so they have a lot of sex alongside the lack of any sort of family planning.
This is obvious in Somalia but similar story in Nigeria.
The government is so corrupt that the population doesn't have employment or any recreational activities to do. The governments also seem to be against family planning, which is common in Africa meaning the average citizen doesn't have access to means to prevent pregnancy leading to a higher birthrate thus a higher population over time.