The boom in oil money helped crown Angola’s seaside capital, Luanda, as the world’s most expensive city. Angola was once a magnet for the world’s biggest oil companies, drawing billions of dollars in investment from BP PLC, Exxon Mobil Corp. XOM 0.13% and others back when crude prices were rising to $100 a barrel. Now, foreign companies have all but given up on new ventures there. BP PLC partially pulled out of an offshore block, taking a $750 million write-down this year. Halliburton Co. HAL 1.22% and other oil-service companies blamed falling revenue on declining activity in regions including Angola. Total SA of France is reshuffling personnel to cut costs while Italy’s Eni E 0.18% SpA is renegotiating service contracts. Energy companies have reduced capital spending in Angola more than in any other sub-Saharan African country, with an estimated $67 billion in spending cuts from 2015 to 2020, according […]