As the energy shock unleashed by tensions in the Middle East rippled through Africa, a massive oil refinery in Nigeria’s biggest city of Lagos, owned by Africa’s wealthiest man, came to the rescue. Running at its full capacity of 650,000 barrels per day, the world’s biggest single-train refinery supplied fuel to many African countries that usually relied on imports through the Strait of Hormuz, from Senegal in the west to Mozambique in the southeast. Built at a cost of about US$20 billion,...