Nigeria's oil output was at the lowest since 1990 as its crude oil production fell below 1 million barrels per day (bpd) in August 2022. And data from the Organization of the Petroleum Exporting Countries in early September showed that Angola and Libya have overtaken Nigeria as Africa's highest crude oil producers. The Conversation Africa's Wale Fatade asked Omowumi Iledare, professor emeritus in petroleum economics and policy research to explain what's happening.